Activation method using modifying agent

ABSTRACT

The present invention relates to a method of activating an organic coating to enhance adhesion of the coating to a further coating and/or to other entities comprising applying a solvent and a surface chemistry and/or surface topography modifying agent to the organic coating.The invention also relates to a coated substrate having an activated coating, wherein the adhesion of the coating to a further coating and/or other entities has been enhanced by application of a solvent and a surface chemistry and/or surface topography modifying agent to the coating.The invention further relates to an activation treatment for an organic coating to enhance adhesion of the coating to a further coating and/or to other entities comprising a solvent and a surface chemistry and/or surface topography modifying agent and a method for the preparation of the activation treatment.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Divisional of U.S. Nonprovisional application Ser.No. 15/884,206 filed on Jan. 30, 2018, which is a Continuation of U.S.Nonprovisional application Ser. No. 11/784,534 filed on Apr. 5, 2007,which is a Continuation-in-Part of international applicationPCT/AU2006/000070, filed on Jan. 20, 2006, which claims the benefit andpriority of U.S. Provisional Application 60/646,204, filed on Jan. 21,2005, the disclosures of which are incorporated herein by reference intheir entireties.

FIELD

The present invention relates to a method of activating an organiccoating, a coated substrate having an activated coating and anactivation treatment for an organic coating. In particular, theactivation method improves the adhesion of the organic coating tofurther coating layers and/or to other entities.

BACKGROUND

Organic coatings are generally used to protect the surface of materialsfrom incidental damage, abrasion, chemical attack and from environmentalor in-service degradation.

Organic coatings are also used to enhance the aesthetics and/or opticalproperties of an object or component.

The surface properties of many coatings dramatically change on drying,curing and/or aging to become more inert than might be predicted basedon the chemistry of their individual components alone. Whilst thisphenomenon in part provides the coating with chemical resistance, impactstrength, abrasion resistance and durability, it also complicates theprocess of applying additional coating layers, particularly when theyare not applied within a predetermined reapplication window. The sameproblem arises with applying other entities such as sealants, pin holefillers and surfacers such as those used on composite substrates, decalsand logos applied with pressure sensitive adhesives and the like, tosuch coatings. In cases which require the application of additionalcoating layers and/or other entities, a mechanical abrasion or strippingprocess of the coating is generally necessary before the re-applicationprocedure can take place.

In the specific example of aircraft coatings, it is well known thatadhesion will not meet in-service performance requirements when freshlayers of coating are applied over layers which have aged beyond theacceptable reapplication window. The acceptable window may be of theorder of days under ambient conditions or potentially hours undercertain conditions of high temperature or extreme humidity. Once thereapplication window has been exceeded, the standard practice forapplying additional coating layers on aircraft involves mechanicalabrasion of the aged coating.

Both chemical stripping and mechanical abrasion have limitations.Mechanical abrasion is labor intensive, the reproducibility is variable,and it is ergonomically costly due to the highly repetitive andvibratory nature of the work. As such there is a pressing need for thedevelopment of a surface treatment to improve the adhesion of aged orinert industrial organic coatings towards additional coating layers orother entities, for example, adhesives, sealants, fillers, stickers andthe like.

Coating manufacturers have developed a method of improving the procedureof coating stripping through the development of barrier layers andintermediate coats which, for example, protect the primer and conversioncoating of metal structures from the chemical stripping agents (U.S.Pat. No. 6,217,945).

Although this procedure would reduce the amount of infrastructure downtime, it still relies on paint removal to provide a surface which willaccept a fresh coating layer with acceptable adhesion. Haack (Surfaceand Interface Anal, (2000), 29, p 829) investigated the interaction ofautomotive polyurethane coatings using UV light to generate ozone.Promising results in terms of improved adhesion and reduced watercontact angles were produced when paint formulations incorporating Ti02were subjected to H202 and UV light. However, there are obviouspractical difficulties associated with this strategy, particularly interms of its commercial viability for application in areas susceptibleto corrosion and for treating larger surfaces. Also the occupationalhealth and safety issues make it less suited to commercial application.

In the biological field, Park et al. (Biomaterials, (1998), 19, p 851)employed the surface urethane NH group to graft chemical species ontopolyurethane rubber, whilst Levy et al. (Biomaterials (2001) 22, p 2683)employed a strong base to remove the surface urethane NH proton toaccelerate such nucleophilic grafting reactions. Both strategies areunsuitable for activating organic coatings. The chemical reactionkinetics of the first strategy would be too slow to be practical,particularly since, considering the low surface energy and inertness tobonding of such coatings, the urethane NH groups may not be orientedtowards the air-coating interface. The use of very strong bases, as perthe second strategy, may degrade existing paint layers, resulting in amechanically weak foundation for fresh coatings to adhere to.Furthermore, the latter strategy is also unacceptable for activatinglarge areas due to corrosion and health and safety considerations.

Other strategies in the biological field have employed free radicaltechniques to graft molecules onto the surface of biomedicalpolyurethane surfaces (Matuda et al, J. Biomed. Res., (2002), 59, p 386;Eaton et al, Biomaterials, (1996), 17, p 1977) Although commerciallyviable, the main difficulty with this strategy lies in promoting actualgrafting of the substrate.

Controlled glycolysis or aminolysis as described in Polymer Engineering& Science (1978), 18, p 844, and J. Applied Polymer Science (1994), 51,p 675) has very slow kinetics at room temperature and as such is not apractical solution. The use of reagents such as dimethylphosphonate(Polymer Degradation and

Stability, (2000), 67, p 159) is also not appropriate since they arehighly toxic and act too slowly at room temperature.

The strategies disclosed above do not adequately address the need forthe development of a surface treatment to improve the adhesion of agedor inert organic coatings to additional coating layers and/or otherentities. The problems of commercial viability, health and safetyconsiderations, viable kinetics, applicability to small and largesurface areas still remain and need to be resolved.

It is to be understood that, if any prior art publication in thebiological field is referred to herein, such reference does notconstitute an admission of a known application to the field ofindustrial and architectural coatings.

SUMMARY

We have now found a method which allows the activation of organiccoatings to improve their adhesive properties towards further coatinglayers of the same or different type, and/or other entities withoutcompromising coating integrity, via the use of mild reagents andconditions.

The process of activation on aged coatings when they have exceeded theapplication window where adhesion will not meet in-service performancerequirements when fresh layers of coating are applied over layers isalso termed reactivation. Both activation and reactivation will be usedinterchangeably.

The term “mild” in this context refers to chemicals which are not knownto be excessively corrosive, acidic, basic or toxic and are applicablefor use in highly regulated industrial environments. One example of suchan environment is a commercial aircraft paint hangar. Additionally themild reagents used in the preferred application methods do not adverselyaffect the bulk aircraft coatings, or underlying coatings, such asprimers or selectively strippable coatings, or underlying substrates,such as aluminium and composite.

Advantageously, this method no longer requires the traditional methodsof mechanical abrasion or chemical stripping of an organic coating toimprove its adhesive properties towards additional coatings and/or otherentities.

In a first aspect, the present invention provides a method of activatingan aged or inert organic coating to enhance adhesion of the coating to afurther coating and/or to other entities selected from adhesives,sealants, pin hole fillers and pressure sensitive decals or logoscomprising applying a solvent and a surface chemistry and/or surfacetopography modifying agent which facilitates surface reduction, surfacehydrolysis, surface oxidation, surface exchange, light induced surfacemodification and/or adds chemical functionality to the surface of theorganic coating.

In another aspect, the present invention provides a coated substratehaving an activated coating, wherein the adhesion of the coating to afurther coating and/or other entities selected from adhesives, sealants,pin hole fillers and pressure sensitive decals or logos has beenenhanced by application of a solvent and a surface chemistry and/orsurface topography modifying agent which facilitates surface reduction,surface hydrolysis, surface oxidation, surface exchange, light inducedsurface modification and/or adds chemical functionality to the surfaceof the organic coating.

The solvent and the agent may be applied either simultaneously,sequentially or separately. Advantageously, the solvent and the agentare applied to the organic coating simultaneously in the form of anactivation treatment.

The agent may act independently from the solvent or alternatively thecombination of the solvent and the agent may be necessary to affect achange in coating surface chemistry and/or topography.

In a further aspect, the present invention provides an activationtreatment for an organic coating to enhance adhesion of the coating to afurther coating and/or to other entities selected from adhesives,sealants, pin hole fillers and pressure sensitive decals or logoscomprising a solvent and a surface chemistry and/or surface topographymodifying agent which facilitates surface reduction, surface hydrolysis,surface oxidation, surface exchange, light induced surface modificationand/or adds chemical functionality to the surface of the organiccoating.

The invention also provides a method for the preparation of theactivation treatment defined above comprising the step of mixing thesolvent with the surface chemistry and/or surface topography modifyingagent which facilitates surface reduction, surface hydrolysis, surfaceoxidation, surface exchange, light induced surface modification and/oradds chemical functionality to the surface of the organic coating.

DETAILED DESCRIPTION

In this specification, except where the context requires otherwise dueto express language or necessary implication, the word “comprise” orvariations such as “comprises” or “comprising” is used in an inclusivesense, i.e. to specify the presence of the stated features but not topreclude the presence or addition of further features in variousembodiments of the invention.

As used in the specification the singular forms “a” “an” and “the”include plural references unless the context clearly dictates otherwise.Thus, for example, reference to “a solvent” includes mixtures ofsolvents, reference to “an agent” includes mixtures of two or more suchagents, and the like.

The method of the present invention involves activating an organiccoating so as to enhance the adhesive properties of at least the surfaceof the coating towards additional coating layers and/or other entities,for example, adhesives, sealants, pin hole fillers, pressure sensitivedecal or logo adhesives and the like. The term ‘activating’ is used inthis context to mean the improvement of the adhesive properties of theorganic coating relative to the adhesive properties of that coating,prior to application of the solvent and the agent.

The word “coating” is used herein its broadest sense and describesdecorative topcoats; undercoats; intermediate coatings; primers;sealers; lacquers; coatings which are pigmented or clear; coatingsdesigned for specific purposes, such as, corrosion prevention,temperature resistance, or camouflage; coatings which are high gloss,matte, textured, or smooth in finish; or coatings containing specialtyadditives, such as metal flakes.

In general, organic coatings which are cured, dried or aged beyond acertain time period develop resistance to forming strong adhesivelinkages towards other entities. Their surface properties become moreinert than might be predicted, based on the chemistry of theirindividual components alone. Without wishing to be limited by theory, itis believed that this phenomena may result from a reduction in coatingsurface energy and amount of reactive surface functional groups inconjunction with a higher cross-link density as a function of curetime/aging which makes chemical interaction and/or the formation ofstrong adhesive linkages with other entities difficult.

The organic coatings which may be activated include, but are not limitedto, fully or partially cross-linked organic coatings. Examples oforganic coatings include, polyurethane, epoxy, polyester, polycarbonateand/or acrylic coatings, more preferably polyurethane and epoxycoatings. Due to their superior mechanical properties and resistance toabrasion, chemical attack, and environmental degradation, such organiccoatings are widely used to protect infrastructure in the aerospace,marine, military, automotive, and construction industries. Many of thesecoatings show a marked reduction in adhesion to other entities, such asadditional coating layers, adhesives, sealants, pressure sensitivedecals or logos and the like, with increased time of curing and/oraging.

The activation method involves applying the solvent and the agent to asurface of the organic coating. The surface treatment is not aconventional coating such as a primer coating or tie-coat, but rather achemical method of modifying the surface of the existing coating so thatit is more receptive to forming adhesive interactions with furthercoatings and/or other entities.

Without wishing to be limited by theory it is believed that theinteraction of the agent and/or solvent combination with the coatingmodifies the coating surface chemistry and/or surface topography toenable it to be more receptive towards other entities including but notlimited to additional coating layers. Such agents and/or solvents arechosen such that the bulk integrity of the coating and underlyingcoating and substrate structures are maintained.

Suitable agents include those which facilitate chemical and/ortopographical modification of the coating surface such as but notlimited to agents which facilitate surface reduction, surfacehydrolysis, surface oxidation, surface exchange, light induced surfacemodification and/or add chemical functionality to the surface of thecoating.

(a) Examples of agents capable of affecting surface reduction include:

(i) Reductants such as sodium borohydride, potassium borohydride,lithium borohydride, zinc borohydride, calcium borohydride and alkoxy,acetoxy and/or amino derivatives thereof such as sodium methoxyborohydride or lithium dimethylaminoborohydride; sodium cyanborohydride,borane and borane complexes; aluminium hydrides such as lithiumaluminium hydride and diisobutyl aluminium hydride; calcium hydride;sodium hydride; Red Al (sodium bis (2-methoxyethoxy)aluminiumhydride);selectrides such as K-selectride (potassium tri-sec-butylborohydride);sodium dihydro-bis-(2-methoxy) aluminate; sodium borohydride mixed withaluminium trichloride; lithium triethylborohydride; and lithiumtri-tert-butoxy aluminium hydride.

(b) Examples of agents capable of catalysing surface hydrolysis include:

(i) Acids such as organic acids, for example, formic acid, acetic acid,benzoic acid, propanoic acid, malonic acid, oxalic acid and kemp'striacid; and inorganic acids, for example, phosphoric acid.

(c) Examples of agents capable of affecting surface oxidation include:

(i) Oxidants such as trichloroisocyanuric acid, sodium hypochlorite,hydrogen peroxide, potassium permanganate, potassium chromate, periodicacid and lead tetra acetate.

(d) Examples of agents capable of affecting surface exchange ortransesterification include:

(i) metal alkoxides or chelates thereof, such as those outlined in“Alkoxides and alkylalkoxides of metals and metalloids” Mehrotra, R. C.,Inorganic Chemical Actia, Reviews, (1967) p 99, including titanium orzirconium alkoxides or chelates thereof, for example those marketed bycompanies such as DuPont or Gelest, i.e.tetra-isopropyltitanate,tetra-n-propyl titanate, tetra-n-butyltitanate,tetra-2-ethylhexyltitanate, tetraethyltitanate, triethanolamine titanatechelate, tetra-n-propylzirconate, tetra-n-butylzirconate andtriethanolamine zirconate chelate.

(e) Examples of agents capable of affecting light induced surfacemodification include:

(i) Free radical initiators such as initiators which are activated bythe presence of light, preferably visible light induced free radicalinitiators or combinations of free radical initiators with tertiaryamines and/or mono or multi-functional unsaturated species.

Suitable light activated initiators include but are not limited tocamphorquinone and derivatives thereof; benzophenone and derivativesthereof, such as, diethylaminobenzophenone; and phenylphosphineoxidederivatives, such as, Irgacure (CIBA).

Tertiary amine agents include species such as N,N-dimethyl toluidine,N,N-dimethylamino ethylmethacrylate, methylimidazole, NNN′N′tetramethyl-1,4-butanediamine and NNN′N′ tetramethylphenylenediamine.

The multi-functional unsaturated species may be selected from acrylates,for example, hydroxyl ethyl acrylate; methacrylates, for example,polyethyleneglycol monomethacrylate, hydroxyl ethyl methacrylate,glycidyl methacrylate, N,N-dimethylamino ethylmethacrylate,ethyleneglycol dimethacrylate and butane diol dimethacrylate; andacrylamides, for example, hydroxyethyl acrylamide and bis acrylamide.

It will be appreciated that the agents may also be prepared in-situ fromtheir constituent components. For example, LiBH₄ may be prepared in-situfrom NaBH₄ and LiCl and sodium methoxyborohydride from methanol andNaBH₄.

The agent(s) are generally present in an amount more than about 0.001%,preferably more than about 0.01%, and most preferably about 0.01% toabout 20% based on the total weight of the activation treatment, or thecombination of solvent(s), agent(s) and any further optionaladditive(s).

Preferably the solvent and/or agent only interact with the surface ofthe organic coating so that the integrity of the coating is notcompromised.

The solvent may be a single solvent or a combination of two or moresolvents. Preferably the solvent is an organic solvent. Suitable organicsolvents or solvent combinations depend on the surface modifying agentemployed (e.g. (a) to (e) above) and include but are not limited to:

(a) ester based solvents such as ethyl acetate, propyl acetate,isopropyl acetate, butyl acetate, isobutyl acetate, tertiary butylacetate and glycol ether acetates;

(b) ketones such as methyl ethyl ketone, methyl propyl ketone, methylamyl ketone, methyl isoamyl ketone, methyl isobutyl ketone and acetone;

(c) alcohols such as aromatic alcohols, for example, benzyl alcohol;aliphatic alcohols, for example, tertiary butanol, n-butanol, secondarybutanol, isopropanol, n-propanol, ethanol, methanol and cyclohexanol;and glycol ethers, for example, those marketed by Dow under the tradename Dowanol such as, ethylene glycol, polyethylene glycol, diethyleneglycol, triethylene glycol, tetraethylene glycol, propylene glycol,dipropylene glycol, tripropylene glycol and polypropylene glycol andtheir monoethers such as mono-C_(1_6) alkyl ethers including but notlimited to those marketed by Dow under the trade name Downanol E-seriesand P-series glycol ethers.

(d) ethers such as glycol diethers, for example, the di-C_(1_6) alkylethers of glycols such as diethers of ethylene glycol, diethyleneglycol, triethylene glycol, tetraethylene glycol polyethylene glycol,propylene glycol, dipropylene glycol, tripropylene glycol andpolypropylene glycol including but not limited to diethylene glycoldimethylether, dipropylene glycol dimethyl ether or diethylene glycolmethyl butyl ether such as those marketed by Dow under the trade nameDownanol E-series and P-series glycolethers; and cyclic ethers such astetrahydrofuran;

(e) amides such as N-methyl pyrrolidinone;

(f) aromatics such as toluene and xylene;

(g) halogenated solvents such as dichloromethane andtetrachloroethylene; and

(h) water

In view of the toxicity and negative environmental impact of halogenatedsolvents (g), it will be understood that they should be used within theconstraints of environmental, health and safety regulations.

Preferred solvents are ester based solvents such as ethyl acetate,ethoxyethyl acetate, isopropyl acetate and/or tertiary butyl acetate;ketone solvents such as methyl propyl ketone, methyl amyl ketone, methylisoamyl ketone and/or methyl ethyl ketone; alcohols such as ethanol,methanol, ethoxyethanol, n-propanol, isopropanol, butanol, tertiarybutanol and secondary butanol; ether solvents such as C₁₋₆ alkyl ethersor combinations thereof (i.e. mixed ethers) of ethylene glycols andpropylene glycols including but not limited to glyme, diglyme, triglyme,tetraglyme and dipropylene glycol dimethyl ether and cyclic ethers, forexample, tetrahydrofuran; amide solvents such as N-methyl pyrrolidinone;and water.

Preferred solvent combinations include glycol ether acetate combinationssuch as dipropylene glycol dimethyl ether tertiary butyl acetate; ether:alcohol combinations such as diproplyene glycol dimethyl ether:n-propanol, isopropanol, methanol, isobutanol, secondary butanol,tertiary butanol, ethoxy ethanol and/or ethylhexanol; ethylene glycolmonomethyl ether: ethanol, methanol, ethoxyethanol and/or isopropanol;glycols and monoether combinations such asdipropylenegylcol-monomethylether, dipropylenegylcol-monobutylether,and/or dipropylenegylcol; ether combinations such as tetrahydrofuran:triglyme and tetrahydrofuran: dipropylene glycol dimethylether; ketonesand acetate combinations such as methylethyl ketone: ethoxyethyl acetateand methyl amyl ketone: ethoxyethyl acetate; N-methyl pyrrolidinone:ethyl acetate; ethyl acetate: benzyl alcohol; dipropylene glycoldimethyl ether: polyethylene; and methyl propyl ketone: methyl ethylketone. Typical solvent combinations include high and low boiling pointsolvent combinations.

The solvent(s) are generally present in an amount of less than about99.999%, preferably greater than about 70%, most preferably in an amountof about 80% to about 99.99% based on the total weight of the activationtreatment or the combination of solvent(s), agent(s) and any furtheroptional additive(s).

One or more additives and/or inerts known in the art of coatings mayalso be used in the method or activation treatment of the presentinvention. Examples include:

(a) rheology modifiers such as hydroxypropyl methyl cellulose (e.g.Methocell 311, Dow), modified urea (e.g. Byk 411, 410) andpolyhydroxycarboxylic acid amides (e.g. Byk 405);

(b) film formers such as esters of dicarboxylic acid (e.g. Lusolvan FBH,BASF) and glycol ethers (e.g. Dowanol, Dow);

(c) wetting agents such as fluorochemical surfactants (e.g. 3M Fluorad)and polyether modified poly-dimethyl-siloxane (e.g. Byk 307, 333);

(d) surfactants such as fatty acid derivatives (e.g. Bermadol SPS 2543,Akzo) and quaternary ammonium salts;

(e) dispersants such as non-ionic surfactants based on primary alcohols(e.g. Merpol 4481, Dupont) and alkylphenol-formaldehyde-bisulfidecondensates (e.g. Clariants 1494);

(f) anti foaming agents;

(g) anti corrosion reagents such as phosphate esters (e.g. ADD APT,Anticor C6), alkylammonium salt of (2-benzothiazolythio) succinic acid(e.g. Irgacor 153 CIBA) and triazine dithiols;

(h) stabilizers such as benzimidazole derivatives (e.g. Bayer, PreventolBCM, biocidal film protection);

(i) leveling agents such as fluorocarbon-modified polymers (e.g. EFKA3777);

(j) pigments or dyes such as fluorescents (Royale Pigment andchemicals);

(k) organic and inorganic dyes such as fluoroscein; and

(l) Lewis acids such as lithium chloride, zinc chloride, strontiumchloride, calcium chloride and aluminium chloride.

The additive(s) are usually present in an amount of less than about 10%based on the total weight of the activation treatment or the combinationof solvent(s), agent(s) and additive(s).

Specific activation methods forming embodiments of the present invention(which may optionally be used in combination) are as follows:

1. Surface Reduction

This method involves using a solvent and an agent such as a reductant,for example, lithium borohydride to cause surface reduction or breakdown of the organic coating surface. While not wishing to be bound byany theory, it is believed that this method provides reactive entitiesor a suitable morphology to improve inter-coat adhesion with furthercoating layers and/or other entities. Suitable solvent or solventcombinations for use in this method are, for example, ether or alcoholbased solvents and their combinations such as dipropylene glycoldimethylether and isopropanol.

2. Surface Hydrolysis

This method involves using a solvent and an agent such as a carboxylicacid, for example, acetic acid to cause surface hydrolysis or break downof the organic coating. While not wishing to be bound by any theory, itis believed that this method provides reactive entities or a suitablemorphology to improve inter-coat adhesion with further coating layersand/or other entities. Suitable solvent or solvent combinations for usein this method are, for example, ester or amide based solvents such asethyl acetate or N-methyl pyrrolidinone.

3. Surface Oxidation

This method involves using a solvent and an agent such as an oxidant,for example, trichloroisocyanuric acid to cause surface oxidation orbreak down of the organic coating. While not wishing to be bound by anytheory, it is believed that this method provides reactive entities or asuitable morphology to improve inter-coat adhesion with further coatinglayers and/or other entities. Suitable solvent or solvent combinationsfor use in this method are, for example, ester or amide based solventssuch as ethyl acetate or N-methyl pyrrolidinone.

4. Surface Exchange

This method involves exposure of the coating surface with a reagentcapable of interacting (via transesterification or otherwise) withsuitable chemical functionality such as ester and/or urethane moities orotherwise to modify its chemistry or topography such that it improvesthe intercoat adhesion with subsequent coating layers. Suitable solventor solvent combinations for use in this method are, for example, etheror alcohol based solvents and their combinations such as dipropylenegylcol dimethylether and isopropanol or dipropylene glycol dimethyletherand n-propanol.

5. Light Induced Photo-Grafting

This method involves applying an agent such as a visible light activatedfree radical initiator, for example, camphorquinone and an unsaturatedspecies, for example, acrylate or methacrylate to the surface of theorganic coating in a solvent. The influence of visible light causes freeradical reactions to occur which modify the surface of the coating toimprove the inter-coat adhesion of the further coating and/or otherentities. Suitable solvents for use in this method include ketone oramide based solvents such as methyl amyl ketone and N-methylpyrrolidinone. The substrate for the above methods having an activatedcoating may be of any type including metals such as aluminum; compositessuch as carbon fibre reinforced epoxy or glass reinforced epoxy;plastics such as polyimide; elastomers such as polysulfide elastomers;or materials containing glass, wood or fabric. There may also be various“sub” coating layers beneath the coating requiring reactivation such asother decorative coating layers, primers, intermediate layers,conversion or anticorrosion coating layers and the like.

Although polyurethane and epoxy based coatings, particularlypolyurethane based coatings are typical, it will be understood thatother organic coatings may be activated by the method of the invention.

When the solvent and agent are combined and applied in the form of anactivation treatment this may take different physical forms such assolution, suspension, mixture, aerosol, emulsion, paste or combinationthereof. Treatments which take the form of a solution or emulsion arepreferred.

The activation treatment may be prepared by mixing the componentstogether with any mixing equipment known to those skilled in the artsuch as but not limited to stirrers, shakers, high speed mixers,internal mixers, inline mixers such as static mixers, extruders, mills,ultra-sound and gas dispersers. When the activation treatment is in theform of a solution, the solution may be prepared as a concentrate anddiluted before use or prepared ready for use.

The activation treatment or the application of the individual componentsthereof may be applied via any method known to those skilled in the artsuch as but not limited to spray, brush, dip, knife, blade, hose,roller, wipe, curtain, flood, flow, mist, pipette or combinationsthereof Application by spray is typical.

The method of activation may be conducted at ambient temperatures oralternatively at higher temperatures if desirable. The activationtreatment or individual components thereof may be applied to small orlarge areas, to sections of larger parts, components or fullinfrastructure such as infrastructure associated with the aerospace(e.g. aircraft), automotive (e.g. vehicles), marine (e.g. ships),transportation (e.g. trains), military (e.g. helicopter, missile) orconstruction industries (e.g. buildings, factories, floors) The surfacemay have simple or complex geometry or may be at any orientation.Treatment may be conducted once or multiple times prior to interactionwith the separate entity.

The exposure time of the activation treatment on the coating is morelimited by the throughput and applications requirements. As such theexposure time may be short for example one minute or extended forexample 24 hours with no detriment to the integrity of the organiccoating or materials that may be found on the organic coating such assealants, and underlying coating structures and substrates.

The organic coating may remain activated in a non-contaminatedenvironment for extended periods of time. In some circumstances, theactivation treatment can remove contaminants from the surface inaddition to activating the coating.

It may also be preferable to remove excess agent and/or treatmentsolution from the surface. This process may be conveniently carried outby techniques such as solvent or water rinsing; dry, water or solventwiping; air or gas knife; vacuum application; removal by squeegee;and/or natural or forced convection evaporation.

Optionally the water or solvent used to remove excess agent and/ortreatment solution from the surface of the coating undergoingreactivation can contain additives for example to enhance the removalprocess, modify the drying time, or reduce corrosion. Such additivesinclude but not limited to ionic and non-ionic surfactants, detergents,anticorrosion additives and wetting agents such as but not limited tothose described above. The additives may also include cleaning agentscommonly used to clean aircraft such as but not limited to thosemarketed under the trade names Isoprep, Turco, CeeBee, Ridoline, Formulaand Daraclean by companies such as Brulin, Elf Atochem North America,MacDermid, W.R. Grace, McGean-Rohco and Henkel.

After the coating surface is separate entities such as additionalcoating layers or coating details, adhesives sealants, pressuresensitive decals or logos, and the like may be applied eitherimmediately or at a later time, providing the surface remainspredominantly uncontaminated during storage or that the contaminationcan be conveniently removed. The activation solution may need to bereapplied in some cases.

Any suitable method known to those skilled in the art may be used toassess whether the adhesive linkage between the organic coating andfurther coatings and/or other entities is fit for purpose. Such testsinclude but are not limited to ASTM, ISO, and FAA standards, in-housetest methods to simulate in-service performance, in-service performanceitself, and durability testing either actual or accelerated. For thecase of aerospace coatings, test methods based on water impact, such aswhirling arm and the Single Impact Jet Apparatus (SIJA) (MIJA Limited,Cambridge, UK), have been found to be particularly useful for assessinginter-coat adhesion. In these cases, the amount of overcoat removal isrelated to the level of inter-coat adhesion.

For aerospace applications the activation method of the presentinvention offers the advantages of improved flow time for the process ofreactivation, greater reproducibility and consistency over larger areasand between operators, and improved ergonomics of the process leading toreduced vibration or repetitive motion based injuries for completing theprocess of reactivation which added together provide a net cost saving.

DETAILED DESCRIPTION OF THE ABBREVIATIONS

In the Examples, reference will be made to the following abbreviationsin which:

-   AFM Atomic Force Microscopy-   APP Applications-   BAC Boeing Approved Color-   BMS Boeing Material Specification-   c Celsius-   Cl Class-   [ ] Concentration-   DHS Desothane HS-   F Fahrenheit-   F Fail-   FTIR Fourier Transform Infrared-   h Hour-   HH high humidity-   HSS High strength Steel-   IC Intermediate Coating-   LH Low humidity-   IPA Isopropanol-   LiBH4 Lithium borohydride-   MAK Methyl amyl ketone-   MEK Methyl ethyl ketone-   MPK Methyl propyl ketone-   Mn Number average molecular weight-   Mw Weight average molecular weight-   MW Molecular weight-   NBA n-butanol-   NPA n-propanol-   NPZ tetra-n-propylzirconate-   NBT tetra-n-butyl titanate-   NPT tetra-n-propyltitanate-   OH&S Occupational Health and Safety-   p Pass-   PAC CS Pre-Applied Composite Coating System-   Proglyde DMM (abbreviated, proglyde) dipropylene glycol dimethyl    ether-   RH Relative Humidity-   SEM Scanning Electron Microscopy-   SIJA Single Impact Jet Apparatus-   SOLO Spray On—Leave On-   sowo Spray On—Wipe Off-   SOHO Spray On—Hose off-   SS Stainless Steel-   tBAC t-butyl acetate-   TEAZ triethanolamine zirconate-   THF Tetra hydrofuran-   TPT tetra-isopropyltitanate-   WARE Whirling Arm Rain Erosion-   Wt % weight percentage-   XPS X-Ray Photoelectron Spectroscopy

DETAILED DESCRIPTION OF THE DRAWINGS

In the Examples, reference will be made to the accompanying drawings inwhich:

FIG. 1 is photographs showing the impact on different metalalkoxidemodifying agents and concentration on inter-coat adhesion. (Base coat:DHS BAC70846, C2. Base cure condition: 16 h, 120 F, 8% RH. Over-coat:BAC50103, C. Over-coat cure: 4 days, 120 F, 10% RH.);

FIG. 2 is photographs showing SIJA inter-coat adhesion. (Base coat: DHSBAC70846, C2. Base cure condition: 16 h, 120 F, 8% RH. Over-coat:BAC50103, C. Over-coat cure: 4 days 120 F, 10% RH.);

FIG. 3 is showing the impact of modifying agent dwell time onover-adhesion performance.

(Base coat: DHS BAC70846, C2. Base cure condition: 16 h 120 F, 8% RH.Over-coat: BAC50103, C. Over-coat cure: 4 days 120 F, 10% RH.);

FIG. 4 is photographs showing the preliminary stencil interactionresults and corresponding SIJA adhesion.

(Base coat: DHS BAC70846, C2. Base cure condition: 16 h, 120 F, 8% RH.Modifying agent dwell time before overcoat ?h. Over-coat: BAC50103, C.Over-coat cure: 4 days, 120 F, 10% RH.);

FIG. 5 is photographs showing the preliminary stencil interactionresults and corresponding SIJA adhesion. (Base coat: DHS BAC70846, C2.Base cure condition: 16 h. 120 F, 8% RH. Modifying agent dwell timebefore overcoat ?h. Over-coat: BAC50103, C. Over-coat cure: 4 days, 120F, 10% RH);

FIG. 6 is photographs showing the preliminary water soak data: 3×applications each of modifying agent system in IPA. (Base coat: DHSBAC70846, C2. Base cure condition: 16 h. 120 F, 8% RH. Over-coat:BAC50103, C. Over-coat cure: 4 days, 120 F, 10% RH.);

FIG. 7a is a photograph showing SOLO treatment solution application onstencil letter and premask diamond quality (Base coat: DHS BAC70846, C2.Base cure condition: 16 h 120 F, 8% RH. Over-coat: 2 mil DHS BAC50103,C2. Over-coat cure before removal: 16 hr, 120 F.);

FIG. 7b is a photograph showing Effect of solvent combination on stencilletter clarity employing, base coat (DHS BAC70846, C2 with curecondition: 16 h, 120 F, 8% RH), modifying agent (5 wt % NPZ SOLO withdwell time 1 h), and over-coat (1 mil DHS BAC50103, C with curecondition before removal: 16 hr, ambient);

FIG. 7c is a photograph showing Image quality employing no modificationagent or 5 WT % NPZ employing a 20:80 NPA:Proglyde combination. (Basecoat: DHS BAC70846, C. Base cure condition: 3 Cycles of 4 hr, 120 F, 9%RH & 8 hr, 75 F 36% RH. Stencil coat: DHS BAC701 Black, C2.);

FIG. 8 is photographs showing scribe adhesion.

(Base coat: DHS BAC70846, C2. Cure condition: 16 h, 120 F, 8% RH.);

FIG. 9 is photographs showing stencil pull & scribe adhesion base coat.(DHS BAC70846, C2. Cure conditions: 16 h, 120 F, 8% RH. Over-coat: DHSBAC50103, C2, 1 mil. Over-coat cure: ambient.);

Stencil Pull Time (min) Scribe Test Time (h)  5 1 30 2 60 3 90 4

FIG. 10 is photographs showing SIJA inter-coat adhesion (DHS CA8000paint); cure conditions as indicated.

FIG. 11 is photographs showing corresponding WARE results to FIG. 12;cure conditions as indicated.

FIG. 12 is photographs showing SIJA inter-coat adhesion (DHS CA8800paint); cure conditions as indicated.

FIG. 13 is photographs showing SIJA inter-coat adhesion (Eclipse paint);cure conditions as indicated.

FIG. 14 is photographs showing SIJA inter-coat adhesion (DHS CA8000paint); cure conditions as indicated.

FIG. 15 is photographs showing Whirling Arm Rain Erosion data:Modification agent (alkoxide): 5 wt % NPZ in 80% IPA: 20% proglyde;. DHSCA8800:

Basecoat—BAC70846, CTR Thinner, Overcoat—BAC70281, CTR Thinner. DHSCA8000: Basecoat—BAC70846, C Thinner, Overcoat—BAC707, C Thinner.Eclipse: Basecoat—BAC70846, TR109 Thinner, Overcoat—BAC707, TR109Thinner.

Base coat cure conditions as indicated. Overcoat cureconditions: 4 days at 120 F;

FIG. 16a is a photograph showing WARE data using DHS CA8800 paint:Basecoat—BAC707 Gray w/varied thinners, Cure conditions: 3 Cycle Cure—4h, 120 F, 18% RH+8 h, 75 F 70% RH. Overcoat—BAC70846 White w/CTRthinner, Cure conditions: 4 days, 120 F.

FIG. 16b is a photograph showing WARE data using DHS CA8800 paint:Basecoat—BAC707 Gray w/varied thinners, Cure conditions: 3 Cycle Cure—4h, 120 F, 18% RH+8 h, 75 F, 70% RH. Overcoat—BAC51265 Blue w/CTRthinner, Cure conditions: 4 days, 120 F;

FIG. 17a is a photograph showing WARE data: Basecoat—DHS CA8800 BAC70846White w/CTR thinner, Cure Conditions: 3 Cycles of 4 h, 120 F, 18% RH+8h, 75 F, 70% RH. Modification agents (alkoxides)—

5Z-60i: 5 wt % NPZ in 60 wt % IPA and 40 wt % proglyde,5Z-60n: 5 wt % NPZ in 60 wt % NPA and 40 wt % proglyde.Overcoat—DHS CA8800 BAC70281 Gray w/CTR thinner, Cure conditions: 4days, 120 F.

FIG. 17b is a photograph showing WARE data: Basecoat—DHS CA8000 BAC70846White w/C thinner, Cure conditions: 3 Cycles of 4 h, 120 F, 3% RH+8 h,75 F, 12% RH.

Modification agents (alkoxides)—5Z-60i: 5 wt % NPZ in 60 wt % IPA and 40 wt % proglyde,5Z-60n: 5 wt % NPZ in 60 wt % NPA and 40 wt % proglyde.Overcoat—DHS CA8000 BAC707 Gray w/C thinner, Cure conditions: 4 days,120 F;

FIG. 18a is a photograph showing WARE data: Basecoat—Eclipse BAC70846White w/TR-109 thinner, Cure conditions: 3 Cycles of 4 h, 120 F, 18%RH+8 h, 75 F, 70% RH. Modification agents (alkoxides)—

5Z-60i: 5 wt % NPZ in 60 wt % IPA and 40 wt % proglyde,5Z-60n: 5 wt % NPZ in 60 wt % NPA and 40 wt % proglyde.Overcoat—Eclipse BAC707 Gray w/TR-109 thinner, Cure conditions: 4 days,120 F;

FIG. 18b is a photograph showing WARE data: Basecoat-Eclipse BAC70846White w/TR-109 Thinner, Cure Conditions: LH or HH (See below).

Modification agents (alkoxides)—5Z-60i: 5 wt % NPZ in 60 wt % IPA and 40 wt % proglyde,5Z-60n: 5 wt % NPZ in 60 wt % NPA and 40 wt % proglyde.Overcoat—Eclipse BAC707 Gray w/TR-109 thinner, Cure conditions: 4 days,120 F. Basecoat Cure LH: 4 h, 120 F, 3% RH+8 h, 75 F, 12% RH for 3cycles, Basecoat Cure HH: 4 h, 120 F, 18% RH+8 h, 75 F 70% RH for 2 or 3cycles;

FIG. 18C is a photograph showing WARE data: Basecoat—Eclipse BAC70846White w/TR-109 Thinner, Basecoat Cure—LH or HH (See below).

Modification agents (alkoxides)—5Z-60i: 5 wt % NPZ in 60 wt % IPA and 40wt % proglyde, 5Z-60n: 5 wt % NPZ in 60 wt % NPA and 40 wt % proglyde.Overcoat—Eclipse BAC707 Gray w/TR-109 thinner, Cure conditions: 4 days,120 F.First TC Cure LH: 4 h, 120 F, 3% RH+8 h, 75 F, 12% RH for 3 cycles,First TC Cure HH: 4 h, 120 F, 18% RH+8 h, 75 F, 70% RH for 2 or 3cycles;

FIG. 19

Basecoat—DHS CA8000 BAC70846 White w/C thinner, Cure conditions asindicated.Modification agents (alkoxides) with 30 minute dwell:5Z-60n: 5 wt % NPZ in 60 wt % NPA and 40 wt % proglyde,7Z-60n: 7 wt % NPZ in 60 wt % NPA and 40 wt % proglyde,9Z-60n: 9 wt % NPZ in 60 wt % NPA and 40 wt % proglyde.Overcoat cure conditions: 4 days, 120 F.

Overcoats:

DHS CA8000—BAC5004 Blue w/C thinner, Eclipse-BAC5004 Blue w/TR-109thinner,Sky-Hullo FLV-II—900BL004 Blue w/IS-900, Type III thinner;

FIG. 20 is photographs showing the shelf life of metal alkoxidereactivation treatment solutions on adhesion.

FIG. 21a is a graph showing soak and recovery experiments using BMSS-142(polysulfide): Weight change.

FIG. 21b is a graph showing soak and recovery experiments using BMSS-142(polysulfide):Volume change.

FIG. 21c is a graph showing soak and recovery experiments using BMSS-142(polysulfide):Hardness change.

FIG. 22a is a graph showing soak and recovery experiments using BMS1-71,CL1 (EPR) elastomer: Weight change.

FIG. 22b is a graph showing soak and recovery experiments using BMS1-71,CL1 (EPR) elastomer: Volume change.

FIG. 22c is a graph showing soak and recovery experiments using BMS1-71,CL1 (EPR) elastomer: Hardness change. (0089)

FIG. 23a is a graph showing soak and recovery experiments using BMS1-71,CL2 (Silicone) elastomer: Weight change.

FIG. 23b is a graph showing soak and recovery experiments using BMS1-71,CL2 (Silicone) elastomer: Volume change. and

FIG. 23c is a graph showing soak and recovery experiments using BMS1-71,CL2 (Silicone) elastomer: Hardness change. (0090)

FIG. 24a is a graph showing soak and recovery experiments using BMS1-57(Silicone) elastomer: Weight change.

FIG. 24b is a graph showing soak and recovery experiments using BMS1-57(Silicone) elastomer: Volume change.

FIG. 24c is a graph showing soak and recovery experiments using BMS1-57(Silicone) elastomer: Hardness change.

FIG. 25 is photographs showing images of elastomers and sealants onrecovery;

FIG. 26 is a graph and photographs showing immersion results fortitanium;

FIG. 27 is a graph and photographs showing immersion results for 2024T3bare aluminum;

FIG. 28 is a graph and photographs showing immersion results for 2024T3clad aluminium;

FIG. 29 is a graph and photographs showing immersion results for highstrength steel;

FIG. 30 is a graph and photographs showing immersion results forstainless steel.

FIG. 31a is a photograph showing sandwich corrosion results: 1×magnification.

FIG. 31b is a photograph showing sandwich corrosion results: 10×magnification.

FIG. 32 is a graph and photograph showing immersion results for BMS8-79composite material;

FIG. 33 is a graph and photograph showing immersion results for BMS8-256composite material;

FIG. 34 is a graph and photograph showing immersion results for BMS8-256with Metlbond;

FIG. 35 is a graph and photograph showing immersion results for BMS8-276with SM905 composite material;

FIG. 36 is a drawing and photographs showing tapeline experiments:Untreated and treated with various modification agent formulations.

FIG. 37 is a graph showing impact on colour shift for DHS BAC70846treated with various modification agents & not over-coated followingaccelerated exposure according to SAE J1960 relative to specimens leftuntreated and

FIG. 38 is a diagram of the Lab-SYSTEM.

FIG. 39 is photographs showing WARE data.

Basecoat—DHS CA8800 BAC900 clear with F thinner, Cure Conditions: 3 heatcycles (4 h, 120 F, 18% RH and 8 h, 75 F, 70% RH).Modification agent—5% NPZ, 80:20 NPA: ProglydePost treatment of Modification agent—none or tack ragOvercoat—DHS CA8800, white or blue cured for 2 weeks at ambient 72 F,35% RH.

FIG. 40 is pencil hardness data for specimens left untreated prior toovercoat or treated with the modification agent prior to over-coatingboth prior to and following 30 day immersion into hydraulic fluid.

FIG. 41 is Gardner Impact adhesion test results employing nomodification agent or 5 WT % NPZ alkoxide in isopropanol. (Base coat:DHS CA8800 BAC3613 Yellow, CTR thinner. Base cure condition: 3 Cycles of4 hr, 120 F, 12% RH & 8 hr, 75 F 36% RH. Over-coat: DHS CA8800 variouscolors, CTR thinner. Overcoat Cure condition: 2 weeks ambient).

EXAMPLES

The invention will now be described with reference to the followingnon-limiting examples. Although the examples concentrate on coatingsderived from polyurethane chemistries it will be understood that thesame activation methodology could be applied to coatings such as but notlimited to those based on epoxy, acrylic, polycarbonate, or polyestercoatings through the appropriate choice of solvent(s), agent(s) andoptional additives under appropriate activation conditions.

The specific “substrate” the polyurethane topcoat is applied to is notrelevant. Hence the substrate can be metal (eg. aluminium), plastic (eg.polyimide), composite (eg. carbon fibre reinforced epoxy or glassreinforced epoxy) or an elastomer (eg. polysulfide elastomer) Thesubstrate may be finished with surfacing materials, films, elastomers orcoatings.

The polyurethane topcoat layer which requires reactivation may havetopcoat, intermediate or priming layers beneath it and again theselayers are not relevant. Typical examples of build-ups employed in theaerospace industry include:

-   -   Aluminium substrate: cleaned, surface prepared with anodize or        conversion coat, epoxy based primer(s), optionally selectively        strippable intermediate coating layer, and polyurethane topcoat        layers.    -   Epoxy based composite: surface based primer(s), optionally        prepared/cleaned, epoxy selectively strippable intermediate        coating layer, and polyurethane top-coating layers.

The reactivation treatment solution is designed in such a way that itcan be applied under industrial conditions and the integrity of the“substrate” or coating layers beneath the polyurethane coating which isundergoing reactivation are not adversely effected to a point where theyare unsuitable for their intended purpose by interaction of treatmentsolution which may inadvertently come in contact with it for shortperiods.

Example 1: Hydrolysis Surface Activation Method

The example demonstrates that improved SIJA inter-coat adhesion relativeto untreated specimens results from activation of the coating prior toover-coating. Inter-coat adhesion provided in this case is similar tospecimens reactivated by sanding.

Example 2: Oxidation Surface Activation Method

The example demonstrates that improved SIJA inter-coat adhesion relativeto untreated specimens results from activation of the coating prior toover-coating. Inter-coat adhesion provided in this case is similar tospecimens reactivated by sanding.

Example 3 Reduction Surface Activation Method

The example demonstrates that improved SIJA inter-coat adhesion relativeto untreated specimens results from activation of the coating prior toover-coating. Inter-coat adhesion in this case is similar to specimensreactivated by provided sanding.

Example 4: Light Induced Photo-Grafting Surface Activation Method

The example demonstrates that improved SIJA inter-coat adhesion relativeto untreated specimens results from activation of the coating prior toover-coating. Inter-coat adhesion provided in this case is similar tospecimens reactivated by sanding.

Example 5: Reduction Surface Activation Method

The example demonstrates that improved Scribe green adhesion (predictorof possible problems during masking tape removal) relative to untreatedspecimens results from activation of the coating prior to over-coating.Inter-coat adhesion provided in this case is similar to specimensreactivated by sanding.

Example 6: Reduction Surface Activation Method

Stripping study indicated that coatings reactivated by surface reductionmethods strip quicker than specimens sanded prior to over-coating butslower than coatings over-coated without treatment.

Example 7 and 8 Evidence of Surface Chemistry Change

Results indicate that a higher Specific contribution to surface energyresults (γsP), particularly to surfaces activated with the reductionstrategy.

Examples 9 to 33 Reduction Surface Activation Method Examples 34 and 5:Surface Activation Method with Exchange Agents

It is envisaged that suitable combinations of components of theactivation treatment will differ depending on the type of coating to beactivated. The appropriate choice of solvent(s), agent(s), optionaladditives and inerts, and activation conditions will differ depending onthe type of coating to be activated.

General Experimental Detail Painting Conditions and Protocol

Spray painting of many flat panels was carried out employing a Yamaharobotic painting arm incorporating a gravity fed Binks Mach lA automaticspray gun configured with a 94 nozzle. Spray painting was conductedusing an inlet pressure of 40 PSI, a scan rate of 100 mm/s and aspecimen to gun distance of 300 mm. The coating thickness was controlledby the gun's fluid needle control position and scan rates. Theseparameters were adjusted in line with paint thickness measurements andassessed using a Fischer Isoscope (MPOD) on aluminium substrates. Whencoating was completed on composite substrates, the coating layerthickness was estimated by calibration with the isoscope readings fromaluminium panels. An analogous strategy was employed for the applicationof the primers, optional intermediary and topcoat layers. For themajority of the examples, the painted films were over-coated followingtaping through the middle of the coupon with 3M vinyl tape (#471) toform a paint edge on its removal. This edge was the impact target forSIJA (Single Impact Jet Apparatus) analysis.

Spray painting of curved or larger surfaces (eg: rain erosion foils) andsome of the smaller flat panels was typically conducted using a BinksMl-H HVLP gun configured with a 94 nozzle. Occasionally, a similargravity fed HVLP gun or a pressure pot fed HVLP gun was used. In thesecases the aluminium or composite was prepared in the same manner as theflat plates prior to the first top-coat being applied. Following cure ofthe first coating layer the front of the foils were masked (IntertapePolymer Group, PG-777 tape) prior toover-coating to form a leading edgeonce the over-coating was applied and tape removed.

Cure protocols were undertaken in a computer controlled temperaturehumidity chamber, such as a Thermoline Environmental chamber and/or aconventional curing oven.

Table 1 Paint Material Information

For the majority of the examples, the coatings used are listed inTable 1. In the examples, paint companies are generally abbreviated:

PRC-DeSoto International: PRC-DeSoto Akzo-Nobel Aerospace Coatings:Akzo-Nobel

TABLE 1 Intermediate Primer Coat Topcoat Coating Epoxy basedIntermediate PRC-DeSoto primers suitable coat that International: forcomposite or is selectively Desothane aluminium based strippable HS,aerospace Akzo-Nobel Aerospace componenets Coatings: Eclipse, DeftChemical Coating Components Base: CA8000/BxxxxxX such as CA8000/B70846XActivator: CA8000B Thinner 1: CA8000C Thinner 3: CA8000C2 Or Base:CA8800/Byyyy Activator: CA8800Z Thinner 1: CA8800CTR Thinner 2: CA8800CTThinner 3: CA8800CT2, Base: ECL-G-xxxx such as ECL-G-14 (BAC70846)Curing Sol: PC-233 Thinner TR-109 Thinner TR-112; Sky-Hullo FLV-II Base:900YYxxx such as 900BL004 (Blue) Curing Sol: 900X001CAT Thinner: IS-900,TyIII Note: the thinner designation C and C2 are used to indicate therelative rate at which the paint cures. C thinners - standard cure ratewith C2 producing a correspondingly faster cure rate (from incorporationof high catalyst levels into the thinner). For Desothane CA8800 CTR isreduced rate, CT is standard rate and CT2 is fast rate cure thinner. ForAkzo-Nobel fast cure thinner is designated TR-112 and standard thinnerTR-109.

Painting Conditions and Protocol

Substrates were cleaned prior to priming and optionally whereappropriate treated with an alodine type conversion coating or anodized.

Polyurethane topcoats, intermediate and primer layers were mixed andapplied according to the paint manufacture instructions. Primer:

Typical conditions:

-   -   For Composite or aluminium: application of common aerospace        epoxy based primer optionally incorporating additives to aide        corrosion resistance at 0.5 mil (12.5 micron) dry film thickness        (dft) per manufacturer instructions.        Intermediate coat:    -   Optionally application of intermediate coat (IC) that is        selectively strippable at 0.35 mils (10 microns) according to        manufacturer instructions

Polyurethane topcoat:

-   -   Application of polyurethane topcoat (eg: Desothane HS topcoat        containing CA8000/B70846X base (white color of this topcoat also        designated as BAC70846. In examples it is typically designated        as Desothane HS 70846X or DHS BAC70846) at 1.0 to 4.0 mil        (typically 1.0 mil (25 micron)). Painted panels flash off for 1        hour prior to cure and accelerated aging.

Standard cure I accelerated aging conditions Employed for topcoats were:(i) Cure painted panels in oven at 120° F., 5-10% RH (Relative Humidity)for 40 hours, followed by (ii) post cure in a humidity chamber at 120°F. (49° C.) and 50% RH for 48 hours, and then (iii) oven cure at 160° F.for 24 hours. Total cure time was 112 hours. Alternatively other“accelerated” aging protocols were employed as specified in the examplesto render the polyurethane topcoat unreceptive to additional coatinglayers as indicated by poor adhesion under standard adhesion tests eg:120° F. and 2-3% RH for 5 days or 120° F. and 5% RH for 16 hours or asspecified in the examples.

Surface Modification

The solvents and agents used for surface modification were purchasedfrom the MERK and Sigma-Aldrich or Dow Chemical Companies. Purity was ofan Analytical or Laboratory Reagent grade purity. Isopropanol andn-propanol were generally of an anhydrous grade. However, alternativesuppliers and grades of the reagents are known to be available.

TABLE 2 General Activation Protocol Task Strategy Treatment Sprayapplication of the reactivation treatment solution employed a Binks Ml-HHVLP gun with a 92 or 94 nozzle and 20 psi inlet pressure or, onoccasion, a similar HVLP gravity or pressure fed gun or by a floodapplication where indicated. The active agent (eg: reducing agent suchas LiBH₄) was dissolved, dispersed or suspended in the solvent/s at apercentage based on weight and the hence prepared ″reactivationtreatment″ applied to the substrate for a given period Post- Spray onleave on application (SOLO) Treatment Optionally the polyurethanesurface may be ″post″ treated Washed with water (or solvent) a periodfollowing treatment - spray on-hose off (SOHO) or Wiped with anisopropanol, ketone (eg: methyl-propyl ketone) or water soaked cloth -spray on wipe off (SOWO) Re- Samples were over-coated with polyurethanetopcoat either: coating Same day (5 mins to 4 hours after treatment)Some period following reactivation. Unless otherwise specified for SIJAor rain erosion adhesion testing, overcoat thickness was 100 micronemploying Eclipse or Desothl(lf HS coatings cured with standardthinners. Cure conditions were 120 F. under 8-20% RH for at least 48hours unless specified. Scribe test overcoat paint thickness wastypically 25 to 50 microns

Analysis

Table 3 provides the equipment and conditions used for testing foranalytical purposes.

TABLE 3 Testing Equipment & Conditions Equipment Conditions SIJAAdhesion testing was completed using a Single Impact Jet Apparatus(SIJA, Cambridge). The initial equipment was typically configured usinga 0.8 mm nozzle typically and employed 0.22 calibre 5.5 mm CrosmanAccupell Pointed Pellets (#11246). Testing was completed followingimmersion in water for 16 to 18 hours, employing a line laser to locatethe impact position, and using a 45° specimen to impact dropletgeometry. A single water jet was employed at each site to test adhesionwith the pressure employed for the ″shot″ indicated below its impact.The velocity of each individual shot was recorded for futurere f erence, but generally the pressure to velocity conversion is specified below (±25 m/s). Pressure (PSI) Velocity (m/s) L 350  50 610 100 725 200895 Alternatively the impa ct was dictated by a ″dot″ or via thevelocity employed eg. 600 m/s. In some cases the amount of overcoatremoved, and hence the inter-coat adhesion was assessed employing imagean alys is techniques to quantify the area of paint removed. Howeverregardless of the impact velocity relative to the unmodified referencemore overcoat removed corresponded with inferior inter-coat adhesion.Scribe Scribe adhesion was assessed according to (BOEING AdhesionSpecification Standard) BS S7225, Class 5. This adhesion test is a fiveline cross-hatch tape (3M tape, No .250) pulltest. Briefly: Heat agedpolyurethane coatings were reactivated and then over-coated (25-80micron thickness) curing the over-coat for 16 hours at room temperatureand 50% RH. The coatings were then scribed according to BS S7225 (Cl5scribe cross-hatch) and the adhesion test performed. The paint adhesionof specimens are rated on a scale of 10 to 1 with ″10 ″ being no paintremoved and ″1″ being all paint removed. Whirling Rain erosion testingwas completed on a whirling arm Arm Rain rain erosion apparatusemploying a 52 inch zero lift helicopter like propeller run at 3600 rpm.Reference and activated polyurethane topcoat foils were over- coated (85to 120 micron paint thickness) following masking to produce a leadingedge. The foils were attached to the propeller at a distance along thepropeller correlating to a velocity of 380 mile per hour at the midpoint of the foil. The effective rain field density of 2 mm dropletsused during the experiment was 1 inch per hour. After 30 min the impactof rain erosion on the inter-coat adhesion of the foils was evaluatedaccording to a 0.5 to 5 rating correlating with the amount of paintremoved or tear length. The impact of water droplets on the leading edgeof the over-coat formed on removal of the tape during the experimenterodes the over-coating layer relative to the strength of the inter-coatadhesion. (F or Fail or red markings indicate less than acceptableadhesion) Paint Procedure for the complete strip test is described inSAE Stripping MA4872, Annex A, pages 51 to 53. In this Stage anabbreviated version was completed using benzyl alcohol based paintstrippers without thermal cycling to compare how the activated andover-coated specimens to untreated and reference specimens. Agedspecimens (Aluminium or composite substrate) were untreated, sanded, oractivated, were over-coated (60- 75 micron), and cured for40 hours at120° F. The edges were taped with Aluminium tape (such as 3M ScotchBrand No, 425) prior to commencing the test. Stripper was applied every2 hours until the coating was removed. Lifting paint was removed justprior to reapplication of the stripper using a plastic squeegee. ContactContact angle analysis was completed using ″FIRST TEN Angle ANGSTROMS″semi-automated video equipped contact angle analyser. CH₂I₂ and H₂0 wereemployed as the reference solvents to calculate the dispersive (γs^(d))and polar (γs^(p)) contributions to surface energy (γs) through theYoung-Dupre FTIR FTIR analysis was carried out on a BRUKER FTIR/NIRspectrometer or Nicolet Instruments, employing NaCl plates or an ATRKRS-5 TiBr/TiI mixed crystal associated with the microscope. Extent ofsurface contamination was assessed by swabbing the surface with a″Q-tip″ soaked with hexane. Following evaporation of the hexane solutiononto NaCl, powder NaCl plates suitable for FTIR analysis were preparedby compression moulding. SEM SEM analysis of the polyurethanecross-sections were collected on a Oxford Pentafet detector controlledby an Oxford ISIS system. Cross-sections of the samples, prepared with acut off saw appropriate for non-ferrous materials, were mounted in epoxyresin, ground and polished to a 1 micron finish and gold coated. Imagingand x-ray analysis was conducted using a 15 KV accelerating voltage anda 17 mm working distance. EDX analysis was specifically refined forcarbon, nitrogen, oxygen, and chlorine. Hydrogen Activity of reducingagent was determined by employing Evolution Hydrogen Evolutiontechniques. The activity of the reducing agent solution (eg. LiBH4 inProglyde DMM) was determined by measuring the quantity of hydrogenevolved following interaction with dilute aqueous acid. AcceleratedEquipment: Atlas (Xenon Arc) Weatherometer UV Outer filter =borosilicate Inner filter = quartz exposure Light intensity: 0.55 W/m2/nm @340 nm Operation Cycle (SAE J1960): Panels: Desothane HS 70846White Test for: Colour shift of previously reactivated (but not over-coated) panels Reactivation potential of samples conditioned throughaging protocol then a UV cycle. Hydraulic Specimens were tested forcoating pencil hardness fluid prior to immersion into the fluid andrated in exposure hardness according to the following protocol (soft tohard). After 30 days immersion the specimens were re-tested. Valuesreported are the softest pencil that would cut into the paint surface.Hardness Scale (Soft to Hard) 6B 5B 4B 3B 2B B HB F H 2H 3H 4H 5H 6HGardner Both sides of the test specimen were subject to Impact varyingimpact forces in 10 inch pound increments Adhesion using a Gardner 160inch pound capacity impact testing machine with a 0.625 inch diameterhemispherical indenter. Values reported are the highest force recordedthat produced no cracking of paint in either the forward or reverseimpact Maximum impact tested was 80 inch pounds.

Example 1: Hydrolysis Method

SIJA inter-coat adhesion of Desothane HS 70846X white (30±5 μm, CA8000Cthinner) cured 40 hour at 120° F. (9% RH) followed by 48 hour at 120° F.(50% RH) followed by 24 hour at 160° F., activated and over-coated withDesothane HS S601X blue (104±10 μm).

Activation Treatment: 30 min, horizontal application position (IPA wipepost treatment)

Example 2: Oxidation Method

SIJA inter-coat adhesion of Desothane HS 70846X white (30±5 μm, CA8000C2thinner) cured 40 hour at 120° F. (9% RH), followed by 48 hour at 120°F. (50% RH) and 24 hour at 160° F., activated and over-coated withDesothane HS S601X blue (104±10 μm).

Activation treatment time 30 min, (IPA wipe post treatment)

Example 3: Reduction Method

SIJA inter-coat adhesion of Desothane HS 70846X white (30±5 μm CA8000C2thinner) cured 40 hour at 120° F. (5% RH) followed by 48 hour at 120° F.(50% RH) and 24 hour at 160° F., activated and over-coated withDesothane HS S601X blue (104±10 μm).

Treatment 30 min, (SOHO—post treatment).

Example 4: Light Grafting Method

SIJA inter-coat adhesion of Desothane HS 70846X white (30±5 μm,CA8000C-thinner) cured 40 hour at 120° F., (9% RH), followed by 48 hourat 120° F., 50% RH and hour at 160° F., activated 120 min, wiped (IPA)and over-coated with Desothane HS S601X blue (104±10 μm).

Initiator System: Camphorquinone (1% w/w based on acrylate),Dimethyltoluidine (120% w/w based on camphorquinone) system placed underan 2×18W fluorescent desk lamp.

Example 5: Reduction Surface Activation Method—Green Scribe Adhesion

Green (scribe) inter-coat adhesion of Desothane HS 70846X white (30±5 μmCA8000C2 thinner) cured 40 hour at 120° F. (9% RH), followed by 48 hourat 120° F. (50% RH) and 24 hour at 160° F., activated and over-coatedwith Desothane HS S601X blue (68±10 μm, 16 h ambient cure). Greenadhesion rating as per BSS7225.

Example 6 Reduction Activation Method—Stripping Rate Test

-   -   A—Untreated, B—Sanded, C—Treatment with 2% NaBH₄ in ethanol, 30        min

Example 7 Evidence of Surface Energy Change Surface Energy Results forActivated Surfaces Employing a Thermally Aged Desothane HS 70846XSubstrate (CA8000C Thinner)

Surface Energy Contact Angle (mJ/m2) (°) Specific Dispersive TreatmentConditions Water CH2I2 γs^(p) γs^(d) C Thinner Fresh 76.5 39.0 4.2 42.0Aged Untreated 76.2 40.3 4.5 41.3 Aged IPA Wipe 75.8 35.0 4.0 44.0Aged - 2% EtOH/EtOH 37.0 36.6 23.7 43.2 Sodium wash Aged - 1% EtOAc/IPA69.7 29.4 5.8 46.6 Acetic Acid wipe Aged- 2 × 18 W 65.2 43.5 8.5 43.5Camphorquinone fluorescent (1% w/w based desk lamp, on acrylate), MAKwipe Dimethyltoluidine (120% w/w based on Camphorquinone)methylamylketoneFresh—4 hour at 120° F. (approx. 9% RH)Aged—40 hour at 120° F. (approx. 9% RH), 48 hour at 120° F. (50% RH) and24 hour at 160° F.

Example 8: Evidence of Surface Energy Change

Surface energy results for activated surfaces employing a thermally agedDesothane HS 70846 substrate (C2 thinner)

Surface Energy Contact (mJ/m2) Angle (°) Specific Dispersive TreatmentConditions Water CH2I2 γs^(p) γs^(d) C2 Thinner Fresh 71.4 27.6 5.0 47.3Aged Untreated 74.6 45.5 5.7 38.5 Aged IPA Wipe 73.9 36.3 4.9 43.4Aged - 2% EtOH/ 42.6 32.2 19.7 45.3 Sodium EtOH Borohydride wash Aged -1% EtOAc/ 67.9 28.7 6.5 46.9 Acetic Acid IPA wipe Aged - 2 × 18 W 68.627.3 6.0 47.4 Camphorquinone fluorescent (1% w/w based desk lamp, onacrylate), MAK wipe Dimethyltoluidine (120% w/w based on Camphorquinone)Fresh - 4 hour at 120° F. (approx. 9% RH) Aged - 40 hour at 120° F.(approx. 9% RH), 48 hour at 120° F. (50% RH) and 24 hour at 160 ° F.

Example 9

SIJA inter-coat adhesion of aged Desothane HS 70846X white (C2)reactivated under the conditions specified for 30 min (SOHO) andover-coated with Desothane S400X red 3 hours following hose-off withwater.

Treatment Solutions Prepared in Progylde (Dipropylene GlycoldimethylEther).

Results indicated that improved inter-coat adhesion is possibleemploying “mild” reducing agents such as NaBH₄ and LiBH₄.

Example 10

SIJA inter-coat adhesion of aged Desothane HS 70846X white (C2)reactivated under the conditions specified for 30 min(SOHO) andover-coated with Desothane HS S601X blue 3 hours following hose-off withwater.

Treatment solutions prepared in dipropylene glycol dimethyl ether at0.2% concentration. Results indicate that reducing agents with differentstrengths may be employed for the purpose of reactivation.

Example 11

SIJA inter-coat adhesion of aged Desothane HS 70846X white (C2)reactivated under the conditions specified for 30 min (SOHO) andover-coated with Desothane S400X red 3 hours following hose-off withwater.

Treatment solutions prepared in dipropylene glycol dimethyl ether.

Example illustrates that a variety of different concentrations may beemployed to “activate” the surface of polyurethane based coatingstowards over-coating to provide improved adhesion.

Example 12

(i) SIJA Inter-Coat Adhesion of Aged Desothane HS 70846X

white (C2) reactivated under the conditions specified (SOLO) for 3 h andover-coated with Desothane HS 5070X blue.

Treatment solutions prepared in dipropylene glycol dimethyl ether.

Example illustrates that very low concentrations of the reducing agentmay be employed to “activate” the surface of polyurethane based coatingstowards over-coating using a spray on leave on approach.

(ii) Scribe adhesion of aged Desothane HS 70846X white reactivated underthe conditions specified and over-coated with Desothane HS 5070X blue.The overcoat was allowed to cure under ambient conditions for 16 h priorto conducting the test

The example illustrates that excellent scribe adhesion results arepossible employing low concentrations of reducing reagent under variousapplication conditions.

Example 13

(i) SIJA Inter-Coat Adhesion of Aged Eclipse BAC70846 White ReactivatedUnder the Conditions Specified (SOLO) for 3 h and Over-Coated withDesothane HS 5070X Blue.

Treatment solutions prepared in Progylde (dipropylene glycol dimethylether) using LiBH₄ as the reducing agent.

Example illustrates that a variety of different reducing agentconcentrations may be employed to “activate” the surface of polyurethanebased coatings towards over-coating from different manufacturers andpolyurethane chemistries.

(ii) Scribe adhesion of aged Eclipse BAC70846 white reactivated underthe conditions specified and over-coated with Desothane HS 5070X blue.The overcoat was allowed to cure under ambient conditions for 16 h priorto conducting the test

The example illustrates that improved scribe adhesion results werepossible employing low concentrations of reducing reagent to reactivatedifferent types of polyurethane topcoats under various applicationconditions.

Example 14

SIJA inter-coat adhesion of aged Desothane HS70846X white reactivatedwith LiBH4 (0.2 wt %) in the solvent/s specified (SOLO) for 3 h andover-coated with various coloured Desothane HS polyurethane topcoats.

Results indicate that different solvents may be employed forreactivation using reducing agents under appropriate conditions.

Example 15

(i) SIJA Inter-Coat Adhesion of Aged Desothane HS 70846X WhiteReactivated with LiBH4 (0.2 wt %) in Proglyde DMM and Co-SolventSpecified (SOLO) for 3 Hours and Over-Coated with Various ColouredDesothane HS Polyurethane Topcoats.(ii) Example incorporating different alcohols (40%) and alcoholcombinations (20:200).

Results indicate that under appropriate conditions a variety of solventcombinations may be employed for the purpose of reactivation withappropriate reducing agents.

Example 16

SIJA inter-coat adhesion of aged Desothane HS 70846X white (C2)reactivated under the conditions specified for 30 min(SOHO) andover-coated with Desothane S400X red 3 hours following hose-off withwater.

1.0% Li (OCH3)xBH4-x in Proglyde prepared by addition of 0 (x=O), 1(x=1, major component)), 2 (x=2, major component), and 3 (x=3, majorcomponent) equivalents (Eq) respectively of methanol “in-situ”.

Example illustrates that the active agent may be prepared “in situ” andthat reactivation can be conducted in the presence of more than onedifferent type of reducing reagent.

Example 17

SIJA inter-coat adhesion of aged Desothane HS 70846X white (C2)reactivated under the conditions specified for 30 min (SOHO) andover-coated with Desothane S400X red 3 hours following hose off withwater.

Example illustrates that different treatment solution preparationmethods can be employed to manufacture the reduction based reactivationsformulation taking into consideration the different ways in whichreducing agents are packaged and sold commercially. In certaincircumstances the reactive agent may be generated “in situ” if required.

Example 18

Rain erosion adhesion results for Desothane HS 70846X white (C2) aged asspecified. Reactivated using the formulations and treatment timespecified before over-coated with Desothane HS 50103X blue.

-   -   (i) Ageing protocol: 4 h (120F, 2-3% RH). SOLO based        reactivation method    -   (ii) Ageing protocol: 5 Days (120F, 2-3% RH) SOLO based        reactivation treatment    -   (iii) Ageing protocol: 4 h (120F, 2-3% RH) SOHO based        reactivation method    -   (iv) Ageing protocol: 5 days (120F, 2-3% RH) SOHO based        reactivation method

Results illustrate that improved inter-coat adhesion is possible usingreducing agents mixed into various reactivation treatment formulationsand applied under various treatment times and protocols for substratesaged under various protocols.

Example 19

Rain erosion adhesion results for aged Desothane HS 70846X white(C-thinner) applied onto epoxy-carbon fibre composite incorporatingprimer, intermediate and topcoat layers reactivated under the conditionsspecified before being over-coated with Desothane HS S601X blue.

Example illustrates that reactivation of aged polyurethane topcoats canbe completed using the reducing methodology on “composite substrates”incorporating paint lay-ups including selectively strippableintermediate coating layers beneath the polyurethane topcoat.

Note: sanded and untreated reference in duplicate, chemicallyreactivated in triplicate.

Example 20

SIJA inter-coat adhesion of aged Desothane HS 70846X white (C2)reactivated with LiBH₄ (0.2 wt % in Proglyde DMM) for 2 h under the posttreatment conditions specified before being over-coated with DesothaneHS S601X blue.

Example illustrates that various “post treatment” protocols may beemployed depending on the application I process requirements withoutnegatively impacting adhesion.

Example 21

SIJA inter-coat adhesion of aged Desothane HS 70846X white (C2)reactivated with LiBH₄ (0.1 wt % in Proglyde DMM) multiple times 30 minapart under the conditions specified before being over-coated withDesothane HS S601X blue.

Example illustrates that multiple applications of the reactivationtreatment solution does not diminish adhesion performance.

Example 22

SIJA inter-coat adhesion of aged Desothane HS70846X white (C2)reactivated with LiBH₄ (0.1 wt % in ProglydeDMM) for (i) one hour beforebeing subjected to the conditions specified and then washed (water)allowed to dry or (ii) for the treatment time specified before beingover-coated with Desothane HS S601X blue or S400X red.

The example demonstrates that reactivation can be conducted for a short(5 min) or extended period (8 days) and that the reactivated surfaceretains its reactivity towards subsequent paint layers under a varietyof conditions.

Example 23

SIJA inter-coat adhesion of aged Desothane HS 7084X6 white (C2)reactivated with LiBH₄ solutions themselves previously aged underambient conditions for the period specified before being over-coatedwith Desothane HS S601X blue.

(i) Treatment solutions: 0.2% LiBH₄ in Progylde DM+the percentage IPAindicated stored for 50 days before being used to reactivate the agedpolyurethane topcoat.(ii) Treatment solutions: Various LiBH₄ concentrations stored inProglyde DMM/20 tBAC for 90 days prior to application(iii) Treatment solution: LiBH₄ prepared as a stock 0.5 wt %concentration in Proglyde DMM and stored for 6 months. Dilutions to theindicated concentrations and formulations were made just prior toapplication of the treatment solution for the purpose of reactivation ina SOLO format(iv) Rain erosion adhesion data from Desothane HS 70846X white (C) curedat 120F (10% RH) 4 days prior to reactivation and over-coating withDesothane HS S601X blue. NOTE: Reactivated samples in triplicate,benchmark untreated and sanded in duplicate.Treatment solutions (a) Aged for 25 days (b) Aged for 25 days(c) Stock solution in Proglyde DMM aged for 25 days and IPA added justprior to application to provide the given concentration (d) preparedfresh (e) prepared fresh.

Examples illustrate that reactivation treatment solutions stored underambient conditions retain their activity thus providing shelf life andpot-life robustness.

Example 24

Example demonstrates that application of the treatment solution canassist in the mitigation of common surface contaminants (residues),produced by the manufacturing assembly which can reduce both the visualappearance and inter-coat adhesion particularly when the reactivationtreatment solution is applied as a SOHO or SOWO application technique.

(i) Illustration of application of common surface contaminates to thesurface of an aged Desothane HS 70846X white topcoat prior toreactivation and over-coating with Desothane HS 5070X blue.Corresponding SIJA inter-coat adhesion results from contaminantquadrants(ii) SIJA inter-coat adhesion of aged Desothane HS white 70846X topcoatcontaminated with (a) petroleum jelly or (b) Aeroshell 33 prior toreactivation employing 0.1% LiBH4 in Proglyde DMM I 20 tBAC. Activationtreatment left on for (30 minutes) prior to application of thedesignated post treatment conditions specified. Subsequently over-coatedwith Desothane HS S601X blue.(a) Petroleum jelly contaminant

(b) Aeroshell 33

The above example clearly demonstrates that improved inter-coat adhesionand paint appearance may be obtained when the Desothane HS coatingscontaminated with common aerospace residues from manufacturing processesare reactivated prior to over-coating.

(iii) Supporting FTIR evidence for selected contaminants: Samples wereswabbed with a hexane soaked “Q-tip” and the hexane containing sampleabsorbed onto NaCl. Following compression molding of the NaCl intoPlaques, FTIR spectra was obtained.

(a) Petroleum Jelly Contaminant

NOTE: typical absorptions around 3000 cm-¹ for the contaminant wasremoved or reduced following reactivation under the conditions listed.

(b) Aeroshell 33 Contaminant

NOTE: typical absorptions around 3000 cm-1 for contaminant was removedor reduced following reactivation under the conditions listed.

Examples illustrate that the level of contaminate is clearly reduced orremoved following the reactivation treatment.

(iv) Supporting surface energy results for selected contaminantsfollowing no treatment, solvent wipe only and reactivation treatments ofthe contaminated aged Desothane HS 70846X white topcoat under theconditions specified.

Surface Energy (mJ/m²) 0.1% LiBH4 (Proglyde, 2% MEK/MPK tBAc) MEK/ NoTreatment Wipe Only MPK Wipe Dis- Dis- Dis- Contamination persiveSpecific persive Specific persive Specific None 45 4.2 43 3.9 45 8.6Microcut 48 3.2 45 4.2 45 6.9 Catoil 47 2.0 44 2.9 45 6.0 Boelube 37 6.046 3.5 46 5.9 Aeroshell 33 43 2.2 44 2.8 46 8.0 Petroleum 49 3.0 41 3.943 6.5 Jelly

The specific surface energy component of total surface energy issignificantly reduced after contaminants are applied to the surface ofthe aged Desothane HS 70846X substrate. Wiping the surface with justsolvent only marginally improved the specific contribution to surfaceenergy (not back to untreated, non-contaminated) whilst specimensreactivated with LiBH4 under the conditions listed provided asignificant improvement in the specific contribution to surface energyabove that for non-contaminated substrates indicating simultaneouscleaning and reactivation has occurred.

Example 25

(i) Example 25. (i) SIJA inter-coat adhesion of aged Desothane HS 70846Xwhite (C2) reactivated under the conditions specified—one (thinapplication) or two (thicker application) applications followed by waterhose-off after the 30 minute treatment time (SOHO) and over-coated withDesothane S400X. Following cure of the over-coating the samples wereimmersed in Skydrol aviation fluid for a period of 30 days under ambientconditions prior to adhesion testing.

The example illustrates that the inter-coat adhesion between topcoatlayers is resistant to hydraulic fluids.

(ii) SIJA inter-coat adhesion of aged Desothane HS 70846X whitereactivated under the conditions specified (SOLO, 180 min) andover-coated with Desothane HS S601X blue. Following cure of theover-coating the samples were immersed in water under ambient conditionsor placed in a condensing humidity chamber at 120F/98% RH for a periodof 30 days prior to adhesion testing and visual appearance assessment.

Results indicate that excellent inter-coat adhesion was obtained after30 days water soak under ambient conditions or 30 days conditioning at120F and 95% RH. Paint appearance is also acceptable and furtherimproved by either using sediment (precipitate free) treatment solutionsobtained from filtering, or post treatment protocols such as a tack ragwipe, wash (SOHO) or wipe (SOWO) processes.

Example 26

(i) The following example illustrates effects of spray application of0.1% LiBH₄

-   -   Proglyde DMM reactivation solution onto bare polysulfide based        sealant (PRC-Desoto PR1772) that has been applied over primed        carbon fiber reinforced epoxy.

Example illustrates that no lifting, bubbling of the sealant occurs evenat thin sealant thicknesses.

Adhesion of the sealant to the substrate is maintained even throughapplication of rubbing.

(ii) The following example illustrates scribe adhesion results frompolysulfide sealant (PRC-Desoto PR 1772) cured for 4 h before treatmentwith a reactivation treatment solution comprised of 0.1% LiBH₄ inproglyde for the time specified before overcoating with Desothane HSS601X Blue and curing for 16 h under ambient conditions.

The example illustrates that no deleterious effects occur followingapplication of the treatment solution onto the sealant prior toover-coating even when the treatment solution is applied onto onlymoderately cured (young) sealants.

(iii) The following example provide weight change data for polysulfidesealant (PRC-Desoto PR 1772) when immersed into different solvents andreactivation treatment solutions.

(iv) The following example illustrates what impact application of LiBH₄I proglyde reactivation solutions has on selective strippable(intermediate) coating layers applied over primed composite panels.

The example demonstrates that no lifting or dissolution of theintermediate coating layer occurs through interaction of thereactivation treatment solution.

(v) The following examples provide immersion weight change data up to 28days of various aerospace substrate materials in various solvents,typical aerospace paint stripper, and reactivation treatment solutions.(a) BMSS-256—carbon fiber reinforced epoxy (b) BMS8-79—glass fiberreinforced epoxy (c) BMS8-276—carbon fiber reinforced epoxy withMetlborid 1515 adhesive film (d) BMS 8-276 with Surface Master 905adhesive film (e) Various metals, Al-aluminum, Ti—titanium, SS—stainlesssteel, HSS—high strength steel.

The examples demonstrate that the reactivation solutions may beformulated for minimal negative interaction with a range of materialsfrom plastics, composites, elastomers, and metals relative to commonsolvents or chemical formulations often used in industries such as theaerospace sector. In the case of metals, weight loss is withinmeasurement uncertainty

Example 27

The following examples demonstrate the reactivation solution may be usedin conjunction with materials such as stencils and design masks andtapes for the production of decorative painted finishes.

(i) Reactivation (LiBH4 in proglyde:IPA 40:60 SOLO application 30 min)applied onto aged Desothane HS white 70846X topcoat (16 h, 120F, 8% RH)with pre-applied vinyl based stencil prior to painting with Desothane HSS601X blue (C2) cured for 16 h at ambient conditions.

(ii) Reactivation (LiBH₄ in proglyde:IPA 40:60 SOLO application 30 min)applied onto aged Desothane HS white 70846X topcoat (16 h, 120F, 8% RH)with pre-applied vinyl based stencil prior to painting with Desothane HSS601X (C) blue at 120F for 16 h.

Example illustrates that crisp non-distorted designs are maintained evenwhen the treatment solution is applied over the top of the mask.

(iii) Reactivation (0.15% LiBH4 in proglyde:IPA, 30 min, SOLO) appliedonto aged Desothane HS white 70846X topcoat (16 h, 120F) withpre-applied vinyl based stencil prior to painting with Desothane HSS601X blue (C2).

Example illustrates that excellent green adhesion, verified by scribeand stencil pull tests, is possible after 1 h with reactivated samplesunlike untreated and excellent letter clarity is possible across a rangeof stencil pull times.

Example 28

Desothane HS 3613X yellow or S400X red (C2) cured aged under thestandard aging protocol was reactivated using the LiBH₄ concentrationsindicated for 30 min SOLO prior to overcoating with Desothane HS S601Xblue.

The example illustrates that different coloured polyurethane coating maybe reactivated using the reduction strategy.

Example 29

(i) SEM pictures of Desothane HS 70846X white polyurethane coatings both(C) and (C2) aged under the (a) standard cure cycle aging conditions and(b) low humidity conditions (120F, 5 days, 2-3% RH) prior to andfollowing reactivation with 0.1% LiBH4 in proglyde.

Example a illustrates that the surface of the coating looks similarprior to and following reactivation. Example b illustrates that thesurface of the coating looks similar prior to and following reactivation

(ii) Surface energy results for Desothane HS 70846X white polyurethanecoatings both (C) and (C2) aged using the (a) standard cure conditionsand (b) low humidity cure conditions (120F, 5 days, 2-3% RH) prior toand following reactivation with 0.1% LiBH4 in proglyde

Substrate Surface Energy (mJ/m²) Cure Treatment* Dispersive Specific LowHumidity Cycle (5 days, 120 F., 2-3% RH) ″C″ — 44.2 5.4 ′C″ 0.1% LiBH₄43.9 6.3 ″C2″ — 41.5 5.5 ″C2″ 0.1% LiBH₄ 42.4 7.3 Ageing Cycle: 120° F.,5% RH 40 h, (ii) 120° F. 50% RH 48 h, and (iii) oven cure at 160° F. for24 h ″C″ 43.6 3.6 ″C″ 0.1% LiBH₄ 45.4 5.9 ″C2″ 45.2 4.2 ″C2″ 0.1% LiBH₄45.5 7.3

Example illustrates that increases in the Specific contribution tosurface energy results from exposure to the reactivation treatmentsolution for the coatings aged under difference conditions and withcatalyst levels (eg: C and C2).

(iii) FTIR-ATR results from Desothane HS 70846X white polyurethanecoatings (C2) aged under the standard conditions and reactivated asindicated.(iv) SEM cross section images of cured aged Desothane HS 70846X white(C2) applied over primer and aluminium substrate (a) untreated, (b)sanded and (c) reactivated using 0.1% LiBH4 in proglyde 30 min SOLOprior to over-coating with Desothane HS S601X blue.

Examples illustrate that the over-coat does not wet the aged Desothanecoating when untreated providing de-bonded regions. The de-bondedregions are not present in the sanded and. chemically reativatedsamples, providing evidence for improved interfacial interaction betweenthe two polyurethane topcoat coating layers (white and blue).

Example 30

Example illustrates the impact of accelerated UV exposure on agedDesothane HS 70846X polyurethane coating relative to untreated referencefor different lengths of exposure time.

(i) Change in colour for samples not over-coated

The example illustrates that the colour shift is similar for samplesuntreated, sanded, reactivated with 0.1% LiBH4 in proglyde that iseither removed after 30 min (SOHO) or not removed (SOLO) if left notover-coated prior to various lengths of accelerated UV exposure time.

(ii) SIJA inter-coat adhesion results for Desothane HS 70846X white (C2)aged under the standard protocol and then accelerated UV conditions for630 h before reactivation and over-coating with Desothane S601X.

The example illustrates that the reactivation protocol provides improvedinter-coat adhesion for samples exposed to accelerated aging and UVexposure with similar result provided to those samples not exposed toUV.

This example is relevant to polyurethane coating that has undergone UVexposure for extended periods before requiring reactivation andover-coating, for example, in-service airplanes.

Example 31

Example shows a comparative paint stripping experiment between compositepanels incorporating a primer, intermediate and polyurethane topcoatlayers. In the example the stripping behaviour of aged Desothane HS70846X white (C2) reactivated with the reduction method under theconditions listed prior to over-coating with Desothane HS S601X relativeto untreated and sanded references.

The example illustrates that the chemically reactivated samples, stripin a similar time frame to the sanded and untreated references.

t=initialTop row (from left to right): 17, 18, 19, 20Bottom row (left to right): 21, 22, 23, 24

17—Untreated 18—Sanded

19, 20—0.05% Lithium Borohydride t-Butyl Acetate: Proglyde 2:98 (SOHO)21, 22—0.01% Lithium Borohydride t-Butyl Acetate: Proglyde 2:98 (SOHO)23, 24—0.05% Lithium Borohydride t-Butyl Acetate: Proglyde 2:98 (SOHO)

The example illustrates that the chemically reactivated samples strip ina similar time frame to the sanded and untreated references.

Example 32

The following example shows the impact on paint adhesion and appearanceof Desothane HS S601X applied over untreated and reactivated agedDesothane HS 70846X coatings (themselves applied over primed aluminum)under cycling temperature and humidity for 500 cycles.

(i) Scribe adhesion was rated “10” for all samples

(ii) SIJA adhesion testing provided improved inter-coat adhesion similarto sanded following the cycling protocol.

(iii) No change of paint finish was noted in terms of “micro-cracking”or “pin head defect formation” following the cycling

The examples illustrate that no apparent reduction in adhesion orover-coat appearance occurs following cycling of temperature andhumidity.

Example 33

Example demonstrates the paint adhesion and overcoat paint quality ofrain erosion foils following simulation of typical paint masking hangaroperations and heat cure. The examples show rain erosion foils,(incorporating primer, intermediate coating, and) topcoated withDesothane HS CA8000/B70846X base with C thinner cured/aged for 5 days at3% RH and 120° F. which were reactivated for 1.5 hours using SOHO (priorto wash off) or the SOLO process indicated.

Following reactivation the samples either underwent a 6 hour 120Fthermal cycle directly (then left under ambient conditions overnight) oralternatively prior to the thermal treatment were wrapped with Kraftpaper or had 4 bands of masking tape perpendicularly wrapped around thesamples. After removal of the paper and tape (wiping the tape lines withIPA) the samples were painted with Desothane HS CA8000/B50103 base withC thinner and following cure tested for adhesion and paint appearancerelative to unreactivated and sanded controls.

(i) SOHO Reactivation

(ii) SOLO Reactivation

Results indicate:

-   -   All the foils except for a random SOLO foil passed with good        marks    -   Excellent paint appearance was noted: No ghosting seen from the        tape being on the foil that was cured for 6 hours and then being        solvent wiped with IPA and no deleterious effects from        application of Kraft paper were noted    -   No significant difference from a 1 application situation and a 3        application situation

Example 34

The following example illustrates the inter-coat adhesion of agedDesothane 70846X and S400X red untreated and reactivated withtetraisopropyl titanate or sanded reference prior to over-coating withS601X blue and 5070X light blue.

(i) SIJA Adhesion

The example illustrates that treatment of the aged surface withtetraisopropyl titanate provides improved adhesion with differentcoloured aged polyurethane substrates and over-coatings.

(ii) The following example demonstrate the reactivation solution basedon tetraisopropyl titanate may be used in conjunction with materialssuch as stencils and design masks and tapes for the production ofdecorative painted finishes.

Untreated Reference

5% Tetraisopropyl Titanate in IPA

The example illustrates that the use of the treatment solution based ontetraisopropyl titanate applied as a treatment solution for agedDesothane HS 70846X prior to over-coating with Desothane HS 5070Ximproved adhesion compared with the untreated reference and alsoprovided minimal letter swelling or figure distortion, when it isapplied SOLO directly over the design stencil prior to over-coating withpolyurethane.

Example 35

Screening experiments assessed a variety of metal alkoxide modifyingagents with different relative reactivities (moisture stabilities) asdescribed in Table 4.

Initial experiments employed SIJA methods to probe the change ininter-coat adhesion with (i) the type of metal alkoxide used in theactivation treatment system and (ii) its concentration. Under allconditions a SOLO approach was employed. FIG. 1 provides the SIJA dataemploying 0.5, 3 and 5 wt % concentrations of modifying agent. It shouldbe pointed out that (i) there was no true concentration parity in theexperiment although given the large concentration range investigatedtrends in performance could be assessed and (ii) all solutions wereprepared in the one solvent system (IPA) to simplify the experiment eventhough it is known that alcoholysis is possible to provide mixedalkoxides. However, to counter this effect to some degree each solutionwas prepared freshly and applied directly. Considering that NPZ has ahigh molecular weight and was supplied as a 70% NPA solution the actualconcentration was much lower than for similar titanium based reagents.

Metal alkoxides with small alkoxy groups (eg: TPT, NBT, NPZ see Table 4)appeared to provide limited benefit at concentrations of 0.5 wt % butunder the reactivation conditions employed showed improved inter-coatadhesion at concentrations above 3 wt %. A lower reactivity for TEAZ wasobserved probably due to its greater moisture stability (Table 4).Closer investigation of concentration (FIG. 2) indicated that around 6-7mmol of modifying agents per 100 g was required to see paint removalcomparable to sanded specimens with less paint removed as theconcentration was increased.

A preliminary investigation was also undertaken to assess the activityof the substrate over time considering that along with a standardreactivation time (eg 30 to 60 minutes) there may also be a requirementin the paint hangar for the activated surface to remain active after aheat cycle or for shorter or longer periods. Preliminary assessmentresults are provided in FIG. 3. The salient points from this study werethat (i) NPZ treatment solutions appear to build up adhesive forcesfaster than TPT, (ii) both versions provided about the same level ofintercoat adhesion after 1 h even though the respective molarconcentration of NPZ was less, (iii) paint surfaces remain active after24 h at ambient conditions, and (iv) the surfaces remained active aftera heat cycle. Point (i) may be explained by the relative reactivity ofthe materials as provided by their difference in hydrolysis rate (Table4). This type of activation window was considered commerciallyattractive and appeared to provide some flexibility for paint hangarscheduling.

TABLE 4 Properties Of Various Metal Alkoxides Promoter/ Tetra-i-Tetra-n-propyl Tetra-n- Property propyltitanate titanate butyltitanateFormula Ti(O-i-C₃H₇)₄ Ti(O-n-C₃H₇)₄ Ti(O-n-C₄H₉)₄ MW 284 284 340Abbreviation TPT NPT NBT Supply 100% 100% 100% Density 0.965 1.05 1.0(g/mL  

Pour Point +17 (Melt Point) −50 <−70 (° C.) Flash point  

23-60 38 50 Relative 0.5-2.0 0.5-2.0 1.0-2.5 hydrolysis rate (mL  

  Relative moles 3.5 3.5 2.9 at 1 wt in 100  

Formula Zr(O-n-C₃H₇)₄ Zr(C₆H₁₄NO₃)₄ Zr(O-n-C₃H₇)₄ MW 327 683 327Abbreviation NPZ TEAZ NPZ Supply 70% (NPA) 100% 70% (NPA) Density 1.071.34 1.07 (g/mL  

Pour Point −70 — −70 (° C.) Flash point 21-25 >100 21-25 (° C.) Relative0.02 >500 0.02 hydrolysis rate (g/mL  

Relative moles 3.5 3.5 2.9 at 1 wt % in 100 g

indicates data missing or illegible when filed

TABLE 5 Physical Properties of Various Solvents Boiling Vapor point*pressure Flash Point Solvent/Material (QC) (mmHg @ 20° C.) (° C.)Isopropanol (IPA) 82 33 12 n-Propanol (NPA) 97 14.9 22 n-Butanol (NBA)116 4.5 35 Hexanol 156 0.5 59 Ethylhexanol 184 0.36 73 Dipropyleneglycol 175 0.6 65 dimethylether (Proglyde DMM) Methyl ethylketone 80 71−1 (MEK) Methyl propylketone 101 27 7 (MPK) *start of boiling pointrange provided

Based on the results provided for LiBH4 based modifying agents stenciland pre-mask swelling appeared to be more related to the physicalproperties of the solvent system employed rather than the lowconcentrations of the active agent. To confirm this with metal alkoxidemodifying agents a brief study was undertaken with the results providedin FIGS. 4 and 5. As was shown for LiBH₄ treatments in 100% Proglyde DMMextensively swelled the vinyl mask whilst 100% IPA provided no swelling.Since slight swelling began at a ratio of approximately 60:40 IPA:proglyde this ratio was considered a reasonable upper limit for theamount of glycol ether in formulations to be used with stencils. Theeffect of modifying agent concentration for NPZ in NPA or TPT in IPA wasalso undertaken (FIG. 5) with the results confirming that in 100%alcohol at least the concentration range (0.5 to 5.0 wt %) did notappear to negatively impact letter quality.

Preliminary 30 day water soak experiments were also undertaken withspecimens reactivated and then over-coated. One to three applications ofthe modifying agent were investigated to simulate both thin and thickapplications, over spray, multiple passes etc. Generally good over-coatappearance was observed even with high concentrations of TPT or NPZ (5wt %) at 1 to 3 applications (FIG. 6).

Pre-Mask and Stencil Vinyl Swelling

Based on the preliminary results for stencil swelling, full stencil andpremask diamond studies were undertaken. Using 100% IPA or NPA in thesolvent system did not appear to provide appreciable stencil or pre-maskswelling and as such letter clarity was crisp even when the reactivationsolution was applied over vinyl mask materials SOLO (FIG. 7a ) Followingencouraging whirling arm rain erosion results (see later) additionalstencil swelling experiments were undertaken employing 5 wt % NPZ in arange of solvents and combinations (FIG. 7b ). No negative impact wasdemonstrated by using a 20:80 ratio of proglyde DMM to IPA or NPA,although at a 40:60 ratio some slight wicking away from the edges of thestencil was noted. Considering the benefits provided by using a slightlyhigher proglyde concentration in terms of adhesion on thicker paintlayers, this degree of stencil swelling may be acceptable and probablynot observed on pre-mask vinyl considering its lower susceptibility toswelling or when applied for short dwell times (15 min). Alternatively,different solvent formulations can be employed depending on whether theapplication is for stencils which typically uses paint layer thicknesson the order of one mil or premask or large body area applications wherethe paint layer thickness is typically two to five mils.

Tests using a 5 wt % NPZ are provided in FIG. 7C. It should be pointedout that using difficult to remove Chinese characters letter quality wassignificantly improved compared to untreated specimens and there was noappearance of stencil swelling when a 5% NPZ 20:80 proglyde:IPA solventsystem was employed for reactivation.

Adhesion

Leveraging the preliminary results provided in the initial screeningexperiments above, the majority of subsequent experiments were completedemploying a 3 wt % concentration of modifying agent in alcohol basedsolvents. Later, higher concentrations of modifying agent and theaddition of proglyde to the solvent system was found necessary toprovide acceptable whirling arm rain erosion results on thick layers ofpaint in certain circumstances. It should also be emphasised that asindicated in FIG. 2, concentration parity was not maintained between TPTand NPZ with a 3 wt % solution actually corresponding to a 10.5 and a6.6 mmol/100 g concentration respectively.

Scribe Adhesion

Various scribe adhesion test results are provided in

FIG. 8. Although the 3.5 h, 120F cure stencil results did not provide areference material that failed BSS7225 (and as such it was not possibleto discriminate between the reactivation treatments) the 12 h ambientcure overcoats did with the reactivated samples providing a “10” ratingsimilar to sanded for in contract to untreated with a “0” rating.

Stencil pull and scribe adhesion were also undertaken (FIG. 9) andmirror that completed for LiBH₄. Regardless of the treatment dwell (30or 90 min), the treatments provided excellent scribe results (10 in BSS7225) after 60 min under ambient conditions superior to that of bothsanded (8) and untreated (3). In terms of stencil pull: pull times of 90min (more severe) did provide a “thinner” letter for all thereactivations treatments. Results for TPT were somewhat superior to NPZregardless of whether IPA or NPA was employed which might be attributedto the difference in effective concentration. However, stencil pullresults were on the whole far better than untreated with effectively afull letter present at a stencil pull time of 60 min (similar to sandedspecimens) whereas untreated specimens only provided a full letter at apull time of 30 min.

SIJA and Rain Erosion Adhesion

Based on those strategies WARE foils were prepared with the main aim of(i) obtaining concentration parity between TPT and NPZ, (ii) employingDesothane CA8000 base coat cured with standard “C” thinner, (iii)exploring the potential for using proglyde as a co-solvent, and (iv)probing the effect of multiple applications. In all the experiments arelatively long application time was employed (4 h) to provide asufficient time frame for the metal alkoxide to firstly react and thencondense with the aged paint surface. Subsequent tests demonstrated thatmuch shorter dwell (application) times, e. g. 30 minutes, were feasible.

The results from SIJA panels are provided in FIG. 10 and the WAREresults obtained from foils provided in FIG. 11. Although reasonablepaint removal was obtained for the untreated reference from the 16 h,120F heat cycle cure (at 8% RH or 0.59 wt % air moisture), the 72 hrbasecoat ambient cure (at 60% RH or 1.12 wt % air moisture) provided anuntreated reference with only marginal paint loss. As such it was againdifficult to compare the relative performance of the reactivationtreatments. Table 6 provides tabular data for the WARE results given inFIG. 11. All foils produced “passes” with the “C” cured base coatingunder the 16 h, 120F, 8% RH cure. For the ambient cured foils, all theNPZ foils had superior WARE compared to the TPT foils. Fot the TPTfoils, multiple applications appeared to help, although incorporation of20% proglyde provided the greatest advantage with ⅔ foils passing thetest (eg a marginal pass). The reason for this is complex: (i) theaddition of proglyde assists in spraying a more uniform treatment film,(ii) proglyde has a much lower vapour pressure than IPA or NPA and assuch the surface remained “wet” somewhat longer which presumably alsoassisted in promoting surface chemical reactions, (iii) proglyde isknown to soften the paint and as such probably promoted metal alkoxidepenetration into the coating surface and hence chemical reactions withembedded chemical groups, and (iv) through that process favors theformation of a surface/subsurface interpenetrating network duringcondensation of the alkoxide prior to or during cure of the over-coat.

TABLE 6 WARE results for FIG. 11 OHS BAC70846 Base coat: 16 h, 120 F.,8% RH, C2, Adhesion promoter 2 h dwell, Overcoat BAC50103, 96 h 120 F.,C2 3% TPT 3% TPT in 3% TPT i IPA PG:IPA, 5% NPZ 5% NPZ Untreated Sandedin IPA x2 1:4 in IPA in NPA 0.5 4.3 4.8 4.6 4.4 4.6 4.5 0.  4.9 4.5 4.84.8 4.0 4.6 4.9 4.8 4.0 4.6 4.7 0.4 4.6 4.7 4.7 4.4 4.4 4.6 OHS BAC70846Base coat: 72 h, 75 F., 60% RH, C2, Adhesion promoter 2 h dwell,Overcoat BAC707, 96 h 120 F., C2 3% TPT 3% TPT in 3% TPT in IPA PG: IPA,5% NP 5% NPZ Untreated Sanded in IPA x2 1:4 in IPA in NPA 2.0 4.9 2.02.4 4.1 4.8 4.8 2.4 4.9 2.3 3.5 3.7 4.5 4.9 2.3 3.3 4.0 4.9 4.9 2.2 4.92.2 3.1 3.9 4.7 4.9

The findings from the trials with Desothane CA8000 on metal alkoxidesmay be summarised generally as follows:

-   -   (i) NPZ is preferred over TPT    -   (ii) NPA is preferred over IPA    -   (iii) Small amounts of proglyde co-solvent appear to be helpful    -   (iv) For maximum benefit, metal alkoxide concentrations should        be >10 mmol/100 g    -   (v) Multiple application provide a more limited benefit    -   (vi) Reactivation of high humidity cured specimens appeared to        be more complex compared with low humidity cure (surface chem.        related/moisture present in coating etc.

Based on those findings a SIJA screening experiment was completed withDesothane CA8800 and Eclipse coatings employing the same two curescenarios albeit that the ambient cure relative humidity was increasedto 80% RH (1.56 wt % air moisture). The results are provided in FIGS. 12and 13. Reactivation employing either TPT or NPZ using a variety ofsolvent systems provided improved levels of inter-coat adhesion underboth cure conditions. The extent of improvement was such that furtherdiscrimination between the alkoxides and solvent systems employed wasdifficult to assess, although introduction of proglyde into theformulation as an 80:20 blend did appear to further enhance theperformance. Further SIJA screening was also completed on DesothaneCA8000 using 5 wt % NPZ and several proglyde to n-propanol andisopropanol solvent ratios as shown in FIG. 14. Results using 5 wt % NPZin a solvent solution of proglyde and either IPA or NPA with 30 to 60minute dwell time of the modifying agent prior to overcoat paint areprovided in FIGS. 15 to 18. FIG. 15 shows the rain erosion resultsemploying a 20:80 proglyde:IPA solution for different dwell times andfor “high” humidity (1.31 wt % air moisture) and “low” humidity (0.22 wt% air moisture) cure scenarios. In all cases the modifying agenttreatment provided excellent inter-coat adhesion to both DesothaneCA8000 and CA8800 coatings with just the high humidity cure Eclipseproviding failures. FIG. 16a explores the effect of Desothane CA8800cure rates using reduced rate (CTR), standard rate (CT), and fast rate(CT2) cured overcoats and a CTR cured base coat employing the samereactivation treatment. For BAC70846 white over BAC707 gray good passeswere obtained for the CTR and CT thinners. The faster CT2 curedover-coat did not provide so good a performance (⅔ foils rated above 4)although it should also be noted that sanded also failed under similarconditions. When BAC51265 Blue was used as the overcoat (CTR) and theBAC 707 gray base coat cured with the different thinners (FIG. 16b ),high passes were obtained for each of the cure rates. This suggests thatreactivation of the basecoat is relatively insensitive to the cure rate(thinner) employed in the basecoat. FIGS. 17a and b documents the effectof higher proglyde concentrations (40%) and the impact of NPA or IPA asthe alcohol in the 5 wt % NPZ formulation using difficult to over-coatsystems including Desothane CA8800 gray on white cured under highhumidity and CA8000 cured under low humidity conditions. In both casesexcellent passes were obtained with little differentiation between thetwo types of alcohols employed.

Given those results the treatments were applied to high humidity curedEclipse base coats which had been previously shown to fail when exposedto 5 wt % NPZ in 80:20 IPA:proglyde (FIG. 18a ) In the case offormulations employing 60% IPA no passes were obtained when three cyclesof the humidity protocol were used even when two application and longeradhesion promoter dwell times were employed although specimens cured atlow humidity were successfully reactivated (FIG. 18b ). Two cycles ofthe high humidity protocol, however, did provide good passes. Incontrast the 60% NPA formulation provided passes with three cycles ofthe humidity cure protocol with ⅔ foils passing after only 1x 30 minapplication and with 2×30 or 60 min treatment solution applications 3/3foils passed the adhesion test (FIG. 18c ). From these results, NPAperformed slightly better than IPA for intercoat adhesion. Thisdifference in NPZ formulations could be due to (i) longer dwell time re:vapour pressure or (ii) mixed alkoxides from the inter action of IPA inthe solvent system not favouring reactivation of such materials.Intuitively one might predict that steric hindrance would be greater inthe mixed alkoxide system which could reduce the reaction rate with thesubstrate surface or ability for it to interpenetrate into the coating.

To determine if higher concentrations of modifying agent would show evenfurther improvements in WARE, NPZ formulations up to 9 wt % (19.8mmol/lOO g) with a solvent of 60 wt % NPA/40 wt % proglyde were testedusing CA8000 basecoat cured at 120F under low (3% RH, 0.22 wt % airmoisture) and moderately high humidity (13% RH, 0.95 wt % air moisture)conditions for eight days. Various paintlines CA8000 (FIG. 19A), Eclipse(FIG. 19B), and Sky-Hullo (FIG. 19C) were used as overcoats. All foils(18/18) passed using 5 wt % NPZ, 13/18 foils passed using 7 wt %, andonly 10/18 passed using 9 wt %. The Sky-Hullo over coat was particularlydiscriminating with 6/6 foils passing using 5 wt %, 4/6 using 7 wt %,and 1/6 using 9 wt %. Overall, the results in FIGS. 19A to 19C suggestedthat the optimum NPZ concentration is near 5 wt % and the optimumalkoxide concentration is near 0.11 mmol per gram.

Preliminary shelf life SIJA data is provided in Figure and suggestedthat the modifying agent was not negatively affected by storage underambient conditions. After three months all of the solutions (stored inglass) were precipitate free indicating a low level of hydrolysis andhence polymerisation. Although the solutions were prepared in either NPAor IPA it was not anticipated that the addition of 20 to 40% proglydewould negatively impact storage stability, particularly since proglydecan be obtained essentially moisture free. Other storage containers suchas high density polyethylene could be used. The modifying solution couldalso be stored as a two part kit, similar to how many aerospace paintsare packaged, where one part would contain the NPZ either at wt % or atdiluted concentration and the second part would containaproglyde/alcohol solvent solution.

Sealant & Elastomer Interaction

Sealant and elastomer immersion results are provided in FIGS. 21 to 24.In those tests BMS5-142 sealant was immersed in modifying agentsolutions with IPA or NPA as the solvent for a period of 24 h, whilstelastomers were immersed for 7 days and the change in weight, volume andhardness monitored both during the immersion as well as on recoveryrelative to MPK and water reference solutions. FIG. 25 provides imagesof the sample following recovery and illustrates that the samples werenot obviously eroded or negatively impacted visually. Considering thatMPK has solubility parameters of [dispersion, polar, and H-bonding][16.0, 9.0 and 4.7 J/cm³], NPA [16.0, 6.8 and 17.4 J/cm³] and employingthe rule of mixtures a 40:60 blend of ProglydelNPA [15.6, 5.0 and 12.0J/cm3], the proglydelNPA solvent blend should not provide a substantialinteraction with these types of materials.

In the case of BMS5-142 (polysulfide non-chromate sealant) weight gainreported in FIG. 21A was more significant for MPK relative to thereactivation treatment solutions and correspondingly the volume changein FIG. 21B was also greater. This result indicated a relatively lowinteraction between the treatments and the polysulfide sealant. After 7days recovery all modifying agent treatment solution immersed sampleswere within 5% of their initial pre-treatment hardness, whilst both thewater and MPK immersed samples were less than 10% softer.

BMSl-71, CLl (EPR) elastomers provided the greatest weight gain in MPKand material appeared to be extracted by the reference solutions. Weightloss on recovery in MPK was about 12% after 7 days compared to less than4% for samples immersed in the treatments. Correspondingly shrinkage onrecovery was greater for the MPK reference, whilst the 7 day recoveryShore hardness at 17% increase was slightly higher than the 9 to 12%increase for samples immersed in TPT or NPZ. Similar results in FIG. 23were provided by BMSl-71, CL2 (Silicone). During immersion, thatmaterial also showed a great uptake of MPK after 7 days (70% weightincrease) compared to the treatment and water solutions (15%), butweight and volume (<5%) and hardness changes (<10%) were all similarduring recovery. BMSl-57 (Silicone) was also less susceptible totreatment solution uptake than MPK (20% weight gain re: 90%). Weight andvolume loss during recovery were less than 10% (typically <5%) for allimmersions, and presumably was caused by material extraction duringimmersion. Hardness increase for the treatment solutions upon recoverywas about 20%, whilst for MPK it was 10%. The larger hardness increasecould indicate a larger sensitivity of this elastomer to the treatmentsolutions than to MPK, a commonly used cleaning component. However, thetreatment solutions are typically sprayed on as thin films rather thanflooded or wiped on as is typical for cleaning solutions so the 7 daysoak of the treatment solutions is an extreme condition.

Metal Interaction

Commonly used aerospace metals were also investigated for weight changeand visual appearance following 30 day immersion in the metal alkoxidesolutions compared with water (FIGS. 26 to 30). As a general pointweight loss or gain was very low (not much more than the resolution ofthe 4 decimal place balance) and generally much less than water whichappeared for most substrates to be the most aggressive. Weight gain fortitanium was less than 0.07% for the treatment solutions re:0.14% forwater although samples in the reactivation solution did appear to bemore “tarnished”. This colour shift was reversed for 2024-T3 aluminiumwith water providing significant discolouration and weight change of1.2% compared with less then 0.1% for the treatments. 2024-T3 cladsamples accumulated a dull finish following immersion in water and lessweight gain compared with the bare Al at just 0.8% increase. Howevertreatment solution samples produced less than a 0.05 wt % increase.Weight gains for high strength and stainless steel immersed in treatmentsolutions were all less than 0.02 wt % and similar to or less than forwater. Interestingly NPZ in IPA did not appear to tarnish high strengthsteel the way the other systems (inc. water) did although thisobservation did not translate into a significant difference in weightgain. Sandwich corrosion was tested according to ASTM Fl 110 with theresults provided in FIG. 31. Without magnification both the referencewater and treatment solutions appear to provide surface discolourationwith outpitting to most of the surface.

Composite Interaction

Immersion results provided in FIGS. 32 for to 35 several relativecomposite systems are to MPK and CEEBEE paint stripper. Samples were cutand immersed without any edge taping and as such, considering the smallsample size, represented a most severe immersion test since the cutedges are regions for easy treatment penetration for example throughpores/fibre-matrix de-bonding from the cutting process and moregenerally from the effective “cut” surface to volume ratio. As generalcomments (i) the CEEBEE paint stripper appeared to be the mostaggressive towards all systems resulting in weight gains in the 1.5 to4% range after a month immersion (ii) generally immersion in thetreatment solution also led to weight gain rather than loss (apart fromBMS 8-276 with SM905), although in such cases the weight change wasgenerally very low (less than 0.5% for all composites and about 0.1% forBMS 8-276 with SM 905. In several instances initial weight gain waslarger (eg 24 hr 7 days) with this reducing after longer periods ofimmersion which may be possible if some material was extracted from thesystem over time or broke off.

Interaction with Tapes

Preliminary tape interaction studies are provided in FIG. 36 and wereconsidered of critical importance to application of the modifying agenttechnology for decorative painting of air craft. In this experiment theeffect of tape line, tape ghosting, and IPA wipe to remove residue wereevaluated. In general no more paint wicking was observed for samplesreactivated prior to/following taping with generally crisp lines presentregardless of the modifying agent formulation applied. With TPT a largeramount of modifying agent residue was expected considering its effectiveconcentration at 5 wt % was larger than the NPZ examples (17.5 mmol/lOOg re:11 mmol/lOO g). However no appreciable ghosting effects wereobvious meaning that even a 1 mil overcoat thickness was sufficient tohide the tape lines.

Interaction with Coatings

During production there remains the potential for paints to bereactivated (eg through over-spray) but not over-coated. Consideringthat the process of reactivation modifies the surface of the paint,there remains the potential for some accelerated aging brought about viaenvironmental factors such as heat, water and UV irradiation. To assessthis, coupons painted with a white basecoat were subjected toaccelerated aging according to SAEJ1960 protocols employing aweatherometer. FIG. 37 provides the change in colour (delta E) over timefor coupons treated with modifying agent, sanded, or untreated relativeto an untreated, painted coupon stored in the dark and measured at eachtime increment. Both untreated and sanded, UV exposed samples showedcolour shift values in the range of one delta E unit during theexperiment. As expected treated coupons at zero time show some colourshift compared the untreated coupon at zero time. Samples reactivatedwith titanium were slightly lighter and had a yellow/green colour shiftprior to exposure. On exposure residue treatment not well bonded to thesurface would be anticipated to be removed (washed away) due to the SAEJ1960 protocol. This can account for the rapid change in delta E afterthe equivalent of three months exposure. However, in both 3/6 monthcases the samples were shifted darker and after an initial drop in theyellow shift became more yellow at 6 months.

Generally speaking colour shifts for Zr based modifying agents were lessthan the Ti based one. With increasing exposure leading naturally to aslight darkening and yellowing of the coating not dissimilar inmagnitude to untreated samples.

Further Performance

Further application of the modification agent is provided in FIGS. 39 to41. FIG. 39 provides WARE results for clear coated samples (eg paintswithout pigment) either treated or non-treated prior to over-coating aswell as the implication of the effects of any post-treatment processsuch as wiping with a tack rag prior to over-coating. In all cases thespecimens treated with the modification agent provided superiorinter-coat adhesion and on some occasions superior to sanded.

FIG. 40 provides hardness measurements prior to and following immersionin hydraulic fluid. The results indicated that the adhesion promotingmechanism is compatible with hydraulic fluid with pencil hardness valueseither approximately the same as or harder than specimens left untreatedprior to over-coating thus providing another benefit.

FIG. 41 provides Gardner impact test results for treated and untreatedspecimens of various paint thickness. The test is used for predictingthe ability of organic coatings to resist cracking or peeling caused byimpacts producing rapid deformation of the underlying (metal)substrate). The results show that the modifying agent does not increasethe brittleness of the paint and could possibly reinforce the some paintcombinations at lower thickness.

It will be appreciated by persons skilled in the art that numerousvariations and/or modifications may be made to the invention as shown inthe specific embodiments without departing from the spirit or scope ofthe invention as broadly described. The present embodiments are,therefore, to be considered in all respects as illustrative and notrestrictive.

We claim:
 1. A method, comprising: applying a solvent and a surfacemodifying agent to a surface of an aged or inert organic coating tosurface hydrolyze the surface of the aged or inert organic coating. 2.The method of claim 1, wherein the surface modifying agent is an acid.3. The method of claim 2, wherein the acid is an organic acid.
 4. Themethod of claim 3, wherein the organic acid is selected from the groupconsisting of formic acid, acetic acid, benzoic acid, propanoic acid,malonic acid, oxalic acid, and combination(s) thereof.
 5. The method ofclaim 2, wherein the acid is an inorganic acid.
 6. The method of claim5, wherein the inorganic acid is phosphoric acid.
 7. The method of claim1, wherein the modifying agent is present in a composition with thesolvent when applying the solvent and the surface modifying agent to thesurface, wherein the modifying agent is present in the composition in anamount of about 0.001% to about 20% based on the total weight of thecombination of solvent and agent.
 8. The method of claim 1, wherein thesolvent is selected from the group consisting of an organic solvent,water, and combination(s) thereof.
 9. The method of claim 8, wherein thesolvent is an organic solvent selected from the group consisting of anester, a ketone, an alcohol, an ether, an amide, an aromatic, ahalogenated solvent, and combination(s) thereof.
 10. The method of claim9, wherein the organic solvent is an ester selected from the groupconsisting of ethyl acetate, ethoxyethyl acetate, isopropyl acetate,tertiary butyl acetate, and combination(s) thereof.
 11. The method ofclaim 10, wherein the ester is ethyl acetate.
 12. The method of claim 8,wherein the solvent is selected from the group consisting oftetrahydrofuran, N-methyl pyrrolidinone, water, and combination(s)thereof.
 13. The method of claim 12, wherein the solvent is N-methylpyrrolidinone.
 14. The method of claim 8, wherein the solvent is acombination of N-methyl pyrrolidinone: ethyl acetate.
 15. The method ofclaim 1, wherein the aged or inert organic coating is selected from thegroup consisting of a polyurethane, an epoxy, a polyester, apolycarbonate, an acrylic coating, and combination(s) thereof.
 16. Acoated substrate, comprising: a surface hydrolyzed organic coatingdisposed on a substrate, the surface hydrolyzed organic coating formedby application of a solvent and a surface modifying agent to an aged orinert organic coating; and a further coating disposed on the surfacehydrolyzed organic coating, the further coating selected from the groupconsisting of an adhesive, a sealant, a pin hole filler, a decal, alogo, and combination(s) thereof.
 17. The coated substrate of claim 16,wherein the substrate is selected from the group consisting of a metal,a composite, a plastic, an elastomer, glass, wood, a fabric, andcombination(s) thereof.
 18. The coated substrate of claim 16, whereinthe surface modifying agent is an organic acid selected from the groupconsisting of formic acid, acetic acid, benzoic acid, propanoic acid,malonic acid, oxalic acid, and combination(s) thereof.
 19. The coatedsubstrate of claim 18, wherein the aged or inert organic coating isselected from the group consisting of a polyurethane, an epoxy, apolyester, a polycarbonate, an acrylic coating, and combination(s)thereof.
 20. The coated substrate of claim 18, wherein the solvent isselected from the group consisting of N-methyl pyrrolidinone, ethylacetate, and combination(s) thereof.